Editor's note: With the past four Ballon d'Or winners -- Lionel Messi, Luka Modric and Cristiano Ronaldo (twice) -- all over the age of 30 at the time of their victory, and other would-be winners such as Antoine Griezmann, Neymar and Eden Hazard well on the way to veteran status, there has never been a better time for the next generation to take over. So step forward, Kylian Mbappe, Jadon Sancho, Trent Alexander-Arnold and others!

For the second straight year (read the 2019 edition here), ESPN brings you the game's next generation. Some of tomorrow's stars have already made their mark on the big stage -- you might remember what Mbappe did to help France win the World Cup two years ago -- but all of them have one thing in common: They are the top talents aged 21 or under. So who makes the grade, what are their particular qualities and how can they get even better?

Compiling this year's list is Tor-Kristian Karlsen, who has worked as a scout and executive for clubs across Europe, including Monaco, Zenit and Watford. He explains his methodology, before revealing the list.

Why 36?

From an initial "long list" of 75 players, those remaining are the ones who satisfied my two main criteria: appearances at the highest level and confirmed performance level over a sustained period. Chelsea's Reece James, for example, was a contender, but the 20-year-old has made only 12 Premier League starts.

Meanwhile, only the absolute top players born in 2002, such as Ansu Fati and Eduardo Camavinga, were considered, whereas exceptional 2003-born talents -- Rayan Cherki and Jude Bellingham among them -- were noted for future reference.

What types of research were undertaken?

I used a sounding board consisting of professional scouts and sporting directors from several top European clubs before compiling the final ranking, as well as online scouting platforms such as WyScout and InStat. Personal preference also played a significant role.

Is there a reason that attacking players dominate the list?

In general, forwards get more playing time at a younger age than, say, central defenders, who tend to need more time to develop tactical awareness, positioning and understanding of the game. Beyond those who did make it, other defenders considered included Dan-Axel Zagadou, Boubacar Kamara, Jules Kounde, Ozan Kabak and Ibrahima Konate.

Notes:

- Players included must be age 21 or under on May 1. The top 10 have been ranked, with the rest listed in alphabetical order.

- With uncertainty about the coronavirus' effect on the transfer market, valuations are based on the writer's pre-COVID-19 estimations.

- ESPN FC on YouTube: Tor-Kristian Karlsen talks to Gab Marcotti and Julien Laurens

- Stream ESPN FC TV, 30 for 30 soccer stories on ESPN+ (U.S.)

Presenting the best players on planet football, age 21 or under ESPN

Jump to: The top 10 | Aouar | Alexander-Arnold | Camavinga | David | Davies | De Ligt | Donnarumma | Fati | Felix | Foden | Greenwood | Guendouzi | Haaland | Hakimi | Havertz | Hudson-Odoi | Isak | Kulusevski | Malen | Martinelli | Mbappe | Mount | Odegaard | Osimhen | Pulisic | Rice | Rodrygo | Saka | Sancho | Soumare | Tonali | Torres | Upamecano | Valverde | Vinicius | Zaniolo

The top 10

play 1:42 What makes Kylian Mbappe so special Tor-Kristian Karlsen explains why it's so difficult to find faults in Kylian Mbappe, despite his age.

10. Joao Felix (FW; Atletico Madrid / Portugal)

Age: 20

Estimated transfer value: €95m

In terms of culture changes, going from a free-flowing Benfica side to the tactical discipline instilled by Diego Simeone at Atletico Madrid is about as stark as it gets in European football. So it is no surprise that Felix got off to a slow start after arriving in Spain last year, with four goals and one assist in La Liga. However, the talent that saw him cost €126m has not gone away, and he remains a top prospect.

Strengths: As a second striker, he erupts in creativity when on the ball, and when dropping deeper, he is an inventive playmaker. Although Cristiano Ronaldo comparisons are premature and imprecise, it would be a surprise if Felix did not establish himself as a leading performer at the top level. His refined touch excites fans, who also appreciate his fluid, intelligent movements, as well as his dangerous shot and finishing abilities.

How he can improve: Even though his undisputed talent is on show in patches during every game, as with many young talents the search for consistency is his main challenge.

- Kundert: Meet 'new Ronaldo' Joao Felix

Federico Valverde won the Silver Ball at the 2017 Under-20 World Cup. Xaume Olleros/Getty Images

9. Federico Valverde (MF; Real Madrid / Uruguay)

Age: 21

Estimated transfer value: €75m

Valverde arrived in Madrid at age 18 and played for the club's B-team before going on loan to Deportivo for a season that ended in relegation. More disappointment followed when he missed Uruguay's 2018 World Cup squad, but since then he has established himself for club and country. With Luka Modric in the twilight of his career and Toni Kroos very much a veteran himself, Valverde is set to run Madrid's midfield for the foreseeable future.

Strengths: Not only does Valverde possess the technical ability and passing skills to seamlessly slot into one of the world's best midfield units, but he also has the pace and agility to escape crowds and the determination to pose a goal threat. In addition, a tenacity and whatever-it-takes attitude -- as shown by his sending off in the Spanish Supercopa final -- gives his game an edge. Potentially one of the world's top box-to-box midfielders.

How he can improve: Poor decision-making and youthful enthusiasm can tempt him to try audacious attacking runs with the ball, when a more experienced player would keep possession and build from the back.

- Marsden: Valverde decisive as Madrid hold off Atletico

play 1:28 Does Joao Felix deserve to be in the top ten? Tor-Kristian Karlsen explains why Joao Felix is amongst the top ten players under 21.

8. Erling Haaland (FW; Borussia Dortmund / Norway)

Age: 19

Estimated transfer value: €90m

This time last year, Haaland was known best as the son of former Premier League midfielder Alfie and had barely featured for Red Bull Salzburg. Many goals later -- he scored nine in one game at the Under-20 World Cup -- he is a star striker for Borussia Dortmund, who signed him in January after activating his €20m buyout clause, and is already being linked with the likes of Real Madrid and Manchester United.

STREAM ESPN FC DAILY ON ESPN+ Dan Thomas is joined by Craig Burley, Shaka Hislop and others to bring you the latest highlights and debate the biggest storylines. Stream on ESPN+ (U.S. only).

Strengths: Haaland plays the centre-forward role with intensity, chasing every ball and showing great speed over medium and long distances. He is very strong and possesses a powerful shot with his left foot. His finishing skills are impressive, too, and give him an end product in front of goal that belies his age.

How he can improve: At 6-foot-4 and over 190 pounds, Haaland should pose a greater aerial threat -- in 11 games for Dortmund, he has not scored a header -- while there is also room for improvement in his hold-up game. If he progresses in those areas and can deal with mounting expectation and non-scoring spells, he could become the most dominant centre-forward of the next decade.

- Karlsen: How Haaland became soccer's most-wanted teenager

Gianluigi Donnarumma was just 17 years and 189 days old when he made his Italy debut in 2017. Emilio Andreoli/Getty Images

7. Gianluigi Donnarumma (GK; Milan / Italy)

Age: 21

Estimated transfer value: €60m

While outfield players might expect to get chances to play in their late teens, the specialized nature of their position means opportunities can be harder to come by for goalkeepers. As such, the fact that Donnarumma debuted for Milan at 16 and has since played more than 200 times for club and country, where he inherited icon Gigi Buffon's position, shows just how good he is.

Strengths: Whereas the physical aspect has never been an issue for a goalkeeper who stands 6-foot-4, Donnarumma has also developed technically; quick to get down and make saves, his distribution is precise and, without being extravagant, he takes an extra touch, when under pressure in possession, to make the right pass. He has also stood out during a period for Milan that has featured on-pitch underachievement and off-field controversy.

How he can improve: His aggressive style works to his advantage most of the time, but he can be prone to overestimating his own reach when dealing with crosses.

- Miller: Donnarumma among the best homegrown stars

Matthijs de Ligt was 17 on his international debut in March 2017, the youngest Netherlands debutant since 1931. Giuseppe Maffia/NurPhoto via Getty Images

6. Matthijs de Ligt (DF; Juventus / Netherlands)

Age: 20

Estimated transfer value: €85m

After playing so well in Ajax's impressive Champions League semifinal run last season, De Ligt had his pick of Europe's top clubs and chose to join Juventus. Life in Italy has not been smooth sailing for the centre-back and his early games featured several errors, but he has started 17 of 26 Serie A matches and will benefit from the guidance of central defensive legends Giorgio Chiellini and Leonardo Bonucci.

Strengths: At his best, De Ligt displays presence and leadership qualities beyond his years. His distribution is excellent, and he is able to dominate both boxes; scoring the derby winner against Torino showed his prowess. He has worked to win doubters over after moving from Netherlands to Italy, and an assured display in the 2-0 win against Inter further showed his progress.

How he can improve: Perhaps too keen to impress at his new club, De Ligt has been uncharacteristically rash in tackles and committed himself too early. When he is composed, though, he is the same defender who made such an impression in the Champions League last season.

- Kuper: Why ambitious De Ligt chose Juventus

play 2:07 How can Haaland still improve? Tor-Kristian Karlsen explains why Erling Haaland still has room for improvement despite his fine form.

5. Kai Havertz (MF; Bayer Leverkusen / Germany)

Age: 19

Estimated transfer value: €95m

Among Havertz's claims to fame is missing a Champions League game in 2017 because of a school exam, but he has done plenty before and since on the pitch -- including becoming the youngest player to make 100 Bundesliga appearances -- to show the talent that will surely see him move to one of Europe's top clubs soon. He has 10 goals and eight assists in all competitions this season.

Strengths: An elegant attacking midfielder, capable of touches that wrong-foot opponents and creating space to play a penetrating pass, Havertz plays with an ease and confidence that almost borders on arrogance. Left-footed, but very comfortable with his right, he never seems hurried and has vision and ability to pick a pass, combined with the stamina to make well-timed runs into the box.

How he can improve: To fulfill his enormous potential, you could argue that Havertz needs to add aggression to his game, especially in terms of winning challenges and recovering balls in midfield.

- Schoenfeld: Everyone knows Havertz is destined for the top

play 1:14 Does Kai Havertz need to leave Leverkusen to progress? Tor-Kristian Karlsen explains what makes Kai Havertz so exciting and discusses where his future lies.

4. Vinicius Junior (FW; Real Madrid / Brazil)

Age: 19

Estimated transfer value: €80m

Given he signed for one of the biggest clubs in the world as a 16-year-old and cost almost $50m in May 2017, Vinicius Junior has been known as a promising youngster for several years and made his Brazil debut in September. He has not yet reached double figures for league starts in a season, but scored the opening goal in El Clasico against Barcelona in early March.

Strengths: His change of pace, balance and rapid movements make him next to impossible to read and stop; many right-backs look silly when they allow too much space. Although Vinicius is not a regular in the Real Madrid starting lineup, his playing time has increased and his display against Barcelona proved he can handle the grandest of occasions. The fact that he is starting to understand that back-heels and trickery are often of little use is another sign of maturity.

How he can improve: Decision-making still remains an issue, as the opening goal against Barcelona showed. Whereas he should have cut the ball back for a better-placed teammate, he instead went for the near-post finish that -- fortunately for him -- was deflected in.

- Hunter: How Vinicius turned the title race in Madrid's favour

Trent Alexander-Arnold made his international debut in June 2018 and was included in England's squad for the World Cup. John Powell/Liverpool FC via Getty Images

3. Trent Alexander-Arnold (DF; Liverpool / England)

Age: 21

Estimated transfer value: €100m

Alexander-Arnold combines effective defending with an ability to set up goals that is unmatched by any other Premier League full-back. He has assisted on 24 goals in the Premier League since the start of 2018-19, and only Kevin De Bruyne has created more chances than his 75 this season, although Alexander-Arnold's most famous assist was surely a quickly taken corner against Barcelona in last season's Champions League.

Strengths: Alexander-Arnold is a gifted all-around footballer, to the extent that he could do an excellent job as a box-to-box midfielder. Not only does he have a good touch on the ball, he can also pass, strike set pieces, cross and shoot with a range and variety of techniques normally reserved for players further up the pitch; his precisely executed switch-of-play ball to Andy Robertson on the opposite flank is a fine example of what he can do.

How he can improve: While full-backs are often singled out for having lost the fine art of defending in one-on-one situations, Alexander-Arnold has made steady progress in this area over the past year.

- Reddy: Why Alexander-Arnold will not stop

Jadon Sancho came through the youth ranks at Watford and Manchester City before moving to Borussia Dortmund in 2017. Getty

2. Jadon Sancho (FW; Borussia Dortmund / England)

Age: 20

Estimated transfer value: €125m

Over the past 12 months, Sancho's form and progress have been so impressive that he is being linked with a $125 million move away from Dortmund, with Manchester United the reported favourites for his signature. He has scored 26 times and assisted 29 other goals in the Bundesliga alone since the start of 2018-19, and the winger's outstanding form has made him a regular in the England team.

Strengths: From mainly playing in bursts, Sancho has grown close to the finished article and capable of influencing throughout a game. Quick, technically proficient and able to score and create goals, he can play on either flank but is even more of a threat when he moves centrally. The ease with which he lays off passes to overlapping full-backs and dinks weighted through balls behind opposing defences make him a joy to watch. Sancho loves playing football, and it shows.

How he can improve: Previously criticised for a lack of tactical discipline, Sancho is becoming more diligent in his defensive work.

- Schoenfeld: Sancho will be a star, on his own terms

Before joining PSG in 2017, Kylian Mbappe scored 27 goals in 60 games for Monaco. Photo by Jean Catuffe/Getty Images

1. Kylian Mbappe (FW; Paris Saint-Germain / France)

Age: 21

Estimated transfer value: €175m

That last year's No. 1 retains the top spot shows that Mbappe has been so good for so long at such a young age. In the two years since helping France win the World Cup at 19, he has scored more than 70 goals for club and country and arguably usurped Neymar as PSG's main man. But with Real Madrid rumours ongoing, how much longer will he remain in Paris?

Strengths: Is there anything he cannot do? Every bit the complete forward -- Mbappe tends to play wide on the right for France and in a more central role for PSG -- he is exceptionally strong and quick. He can finish with power or with skill, he can head the ball, he is tactically disciplined and he reads the game better than most. His movements are smooth, smart and incisive.

How he can improve: There are no sides of his game worth trading, at the risk of ending up with a lesser player.

- Laurens: PSG is Mbappe's team, not Neymar's

The next 26 (in alphabetical order)

Houssem Aouar has nine goals and seven assists in all competitions this season. Catherine Ivill/Getty Images

Houssem Aouar (MF; Lyon / France)

Age: 21

Estimated transfer value: €55m

Inheriting the No. 8 shirt at Lyon might be considered daunting enough, given the distinction with which Juninho Pernambucano wore it for almost a decade, but to take it as a teenager is even more noteworthy. But the jersey has not proven too heavy for Aouar. He has played more than 130 games for the club in all competitions and, in the Champions League, has assisted six goals in 12 matches.

Strengths: Most of Lyon's attacking flow goes through Aouar, who plays with the panache of someone five years his senior and links everything together once he gets on the ball. Though not overly physical, his solid frame makes him hard to knock off the ball. He has an excellent first touch, is never in a hurry, is hard to dispossess and hardly ever gives possession away. He is also adept at finding space in and around the opposing penalty area.

How he can improve: He's 5-foot-9, which is average height for an attacking midfielder and playmaker, and the development of his heading ability has never been a top priority.

Eduardo Camavinga's first senior goal came in December 2019 when he scored for Rennes at Lyon. Tim Clayton/Corbis via Getty Images

Eduardo Camavinga (MF; Stade Rennes / France)

Age: 17

Estimated transfer value: €55m

Born in Angola before moving to France as an infant, Camavinga has burst onto the scene in the past year with a string of impressive displays that has earned him admiring looks from big clubs, not to mention a France Under-21 call-up. Rennes' fine season -- they are third in Ligue 1 -- has been due in no small part to their teenage sensation, who has started 24 of his side's 28 league games.

Strengths: A once-in-a-generation talent who could easily have found a place among the Top 10 despite not turning 18 until November, Camavinga plays with ease and can fill every role in the centre of midfield, though he is mainly used in a defensive role. Never in a rush, he plays mainly with one or two touches and sets off on ball-carrying duties only when necessary. The attention has not gone to Camavinga's head, either, because he remains hardworking and disciplined.

How he can improve: The left-footed teenager is ahead of the normal curve of development even for a top talent; until now, he has done more than can be expected of him.

- Laurens: Camavinga's form has top scouts circling

play 1:36 Is Vinicius Jr. really the fourth best player under 21? Tor-Kristian Karlsen explains why Vinicius Jr. has impressed him enough to secure a top 5 ranking.

Jonathan David (FW, Gent / Canada)

Age: 20

Estimated transfer value: €35m

David was born in New York, grew up in Ottawa and has played all his professional club football in Belgium since signing for Gent in 2018. He starred for Canada at last summer's Gold Cup, leading all scorers with six goals and being named in the tournament best XI, and has since netted 18 goals in 27 games in the Belgian first division.

Strengths: Initially seen as a threat on counterattacks for his pace and direct style, David has developed his game over the past six months and boasts impressive finishing ability. While he is liveliest with smart movements when the ball enters the last third -- in which he often finds pockets of space -- he has also improved his ability to hold the ball up and bring teammates into play.

How he can improve: While David has hardly put a foot wrong and has impressed in the Europa League, his next logical step is a move to a higher competitive level.

Alphonso Davies became the third-youngest player in MLS history when he made his Vancouver debut in July 2016. Getty

Alphonso Davies (DF; Bayern Munich / Canada)

Age: 19

Estimated transfer value: €45m

The former Vancouver Whitecap moved to Germany only in January 2019 and did not make his first Bundesliga start until the end of October, two weeks after he opened the scoring for Canada in a shock win against the United States. Davies' rise as a dynamic left-back for Bayern has been meteoric and a fine performance at Chelsea in the Champions League announced him on the big stage.

Strengths: Converting the onetime winger into a left-back has been a huge success for Bayern, for whom Davies is no less of a threat when he begins offensive surges from a deeper position. Thanks to his pace and athleticism, it is easy to forget that he is also a fine footballer, who comfortably fits into Bayern's possession game with neat close control and quick feet to get out of tight corners.

How he can improve: Davies is learning fast and shows no lack of willingness adapting to the ins and outs of his new role. That said, he is very much reliant on pace to resolve defensive situations, rather than conventional defending.

- Marshall, Bell: Is Davies the best player in CONCACAF?

Ansu Fati scored his first Barcelona goal against Osasuna in August 2019. Xavier Bonilla/NurPhoto via Getty Images

Ansu Fati (FW; Barcelona / Spain)

Age: 17

Estimated transfer value: €50m

Fati was the second-youngest player in Barcelona history when he made his debut at age 16 years and 298 days last August, and just 23 days later, he became the third-youngest in competition history to make a Champions League appearance. Spanish Under-21 honours followed, while no less a judge than Lionel Messi has said that Fati "is a fantastic player and has what it takes to succeed."

Strengths: Equipped with exceptional pace and close control, he is almost impossible to stop when there's space to take on defenders in one-on-one situations. Though mostly recognised for his qualities on the ball, he has already scored a headed goal, and his movement when not in possession is remarkably developed for a player of his age. He does not seem fazed by expectation or the attention he has attracted.

How he can improve: Because he has such faith in his quick feet and ability to take on opponents, he can be caught in possession and give away the ball unnecessarily.

- Lowe: Is Fati the answer for Barcelona, post-Messi?

In December 2017, 17-year-old Phil Foden became the youngest Englishman to start a Champions League game. Matt McNulty - Manchester City/Manchester City FC via Getty Images

Phil Foden (MF; Manchester City / England)

Age: 19

Estimated transfer value: €30m

Foden has been a future star since he was named best player at the 2017 Under-17 World Cup and broke into Man City's first-team squad. He has been used sparingly by Pep Guardiola but has Premier League and cup winners' medals. With David Silva leaving the club, Foden should be set for an integral role at the Etihad Stadium. He might come to be equally important for England.

Strengths: Blessed with a highly advanced footballing brain and wonderful abilities on the ball, Foden is perfectly suited to the patient, sophisticated possession game favoured by Guardiola and most other top European clubs. He might have featured more regularly, but starting at Manchester United in the Premier League was a sign of the regard in which he is held.

How he can improve: Foden's next challenge is to make the permanent transition from an outstanding talent to a fully fledged senior player who can make a 90-minute impact on games.

Mason Greenwood scored his first Manchester United goal 12 days before his 18th birthday. OLI SCARFF/AFP/Getty Images

Mason Greenwood (FW; Manchester United / England)

Age: 18

Estimated transfer value: €30m

When Man United's incredible Champions League win at Paris Saint-Germain is recalled, it might be most significant as Greenwood's debut. In the year since, he has hit double digits for goals, made his England under-21 debut and been called a more natural finisher than Marcus Rashford and Anthony Martial by United manager Ole Gunnar Solskjaer, who compared the teenager to Robin van Persie.

Strengths: In a short sample size, Greenwood, who can play as a central striker or on the right wing, has demonstrated the force and venom of his left foot by scoring some outstanding efforts in the Premier League and in Europe. He is a natural, instinctive footballer, not just for his nonchalant finishing skills but also for his remarkable balance and sublime ball skills.

How he can improve: He has hardly put a foot wrong, but when being played as a centre-forward -- and especially considering his size and athleticism -- he will be expected to pose a greater threat in the air.

Matteo Guendouzi was eligible to represent Morocco, but has pledged his future to France. Photo by James Baylis - AMA/Getty Images

Matteo Guendouzi (MF; Arsenal / France)

Age: 21

Estimated transfer value: €30m

It was a baptism of fire for Guendouzi at the Emirates Stadium, where he made his Arsenal debut against Manchester City a month after arriving at the club. Since then, the former Lorient player has featured in 55 of 66 Premier League games for the Gunners, scored his first senior goal in a Europa League tie and been called into the full France squad, although he has yet to debut.

Strengths: Guendouzi has found things challenging under Mikel Arteta's management, but his potential is still evident. Good at recovering balls from defensive midfield, he takes up smart positions and has a relatively high pass-completion rate: 88% overall in the Premier League, and 81% in the opposition defensive third. At his best, he is an efficient player who is physically strong and covers a lot of midfield ground.

How he can improve: He could benefit from breaking forward from midfield more often and being even more assertive in his pressing game.

At age 19, Achraf Hakimi started all three of Morocco's games at the 2018 World Cup. Alex Gottschalk/DeFodi Images via Getty Images

Achraf Hakimi (DF; Borussia Dortmund, on loan from Real Madrid / Morocco)

Age: 21

Estimated transfer value: €50m

He came through the youth ranks at Real Madrid and remains on the Bernabeu books, but it has been in Dortmund that Hakimi established himself over the past two seasons. A regular creator of chances from his position at right-back, the Moroccan international has 10 assists in 25 Bundesliga games this season, while his four Champions League goals have shown his finishing prowess.

Strengths: His forward runs are full of pace, timing and conviction; indeed, there are few more productive right-backs in European football. During a season in which he has established himself as one of the most exciting players in his position, plenty of top clubs are monitoring Hakimi and wondering whether he will get playing time at Real Madrid.

How he can improve: His tremendous attacking potential means he can leave too much space when charging forward and get caught high up the pitch against teams playing on the break.

At 18 years and 135 days, Callum Hudson-Odoi set a record as the youngest Englishman to play a competitive international. Darren Walsh/Chelsea FC via Getty Images

Callum Hudson-Odoi (FW; Chelsea / England)

Age: 19

Estimated transfer value: €45m

Not 20 until November, Hudson-Odoi has packed plenty in to his career. He was part of England's Under-17 World Cup-winning squad in 2017 and has since risen through the ranks to represent the senior side. At Chelsea, meanwhile, he impressed to the extent that Bayern Munich tried to sign him, only for him to suffer an Achilles injury before committing his future to the Stamford Bridge club.

Top players under 21: Nationality England 8 France 6 Brazil 3 Italy 3 Canada 2 Netherlands 2 Norway 2 Spain 2 Sweden 2 Six countries 1

Strengths: The unpredictable winger, who loves setting off down the left before cutting inside on his favoured right foot, is one of the game's most exciting wide players. Beyond striking characteristics that include a change of pace, quick footwork and being hard to mark in one-on-one situations, he also understands and reads the game, often working out opposing defenders as games develop.

How he can improve: Hudson-Odoi must learn to be more consistent, rather than showing his undeniable ability in patches. He should also add more goals, assists and chances created to his game.

- Williams: Hudson-Odoi repays Chelsea's faith

In a January Copa del Rey win against Real Madrid, Alexander Isak scored two goals and assisted another. Quality Sport Images/Getty Images

Alexander Isak (FW; Real Sociedad / Sweden)

Age: 20

Estimated transfer value: €20m

Isak's story is an example of a next big thing who bounced back after overcoming challenges early in his professional career. Success in Sweden led to a high-profile move to Borussia Dortmund in 2017, but Isak struggled to make an impact. After a goal-laden loan spell at Willem II, he joined Real Sociedad, where he has impressed, often as a substitute.

Strengths: Standing at almost 6-foot-3, the powerful centre-forward is deceptively quick, can finish with both feet and is hard to stop in one-on-one situations. Only 20, he is fast becoming indispensable for Sweden and is finally beginning to realise the undoubted potential that was evident when he emerged several years ago.

How he can improve: Isak tends to score in streaks, and his great runs of form are often followed by lean spells. Though not uncommon for a young forward, it might be a sign that he needs to develop more confidence in his abilities.

Dejan Kulusevski made his Sweden debut in a European Championship qualifier against Faroe Islands in November. Andrea Staccioli/LightRocket via Getty Images

Dejan Kulusevski (MF; Parma, on loan from Juventus / Sweden)

Age: 19

Estimated transfer value: €35m

On loan at Parma from Atalanta during the first half of this season, Kulusevski's form was so impressive that Juventus signed him in January, less than a year after his Serie A debut. He has since been sent back to Parma, where he has five goals and seven assists in 22 league games. That form also saw him earn his first cap for Sweden, against the Faroe Islands in November.

Strengths: A strong-running wide midfielder or forward with power, an intense pressing game and pace to match an excellent left foot, Kulusevski has been compared to Arjen Robben. However, in contrast to the Dutchman, who was initially more of an out-and-out winger with the ability to turn opposing full-backs inside out, the Swede is more about work ethic and strength than finesse, though he does enjoy a touch off his heel and a perfectly weighted through ball.

How he can improve: Not unlike other supremely talented left-footed players, developing his right foot is on his to-do list. Kulusevski also needs to work on how to keep possession in tight spaces.

Last September, Donyell Malen scored all of PSV's goals in a 5-0 win against Vitesse. Photo Prestige/Soccrates/Getty Images

Donyell Malen (FW; PSV Eindhoven / Netherlands)

Age: 21

Estimated transfer value: €35m

One that got away for Arsenal? Malen was on the Gunners' books as a teenager, but moved to PSV in 2017 and has been a prolific scorer ever since; he hit double figures last season and has 17 goals in 25 games in 2019-20. He has also broken into Ronald Koeman's promising Netherlands squad, marking his international debut with the winning goal against Germany.

Strengths: Malen's development over the past year has made many scouts believe he is in the process of outgrowing the Eredivisie. His profile certainly fits the bill for a top European club: He is direct, always looking for the shortest way to goal and quick off the mark. Additionally, he has a sharp finishing technique, possesses excellent dribbling skills and makes incisive runs.

How he can improve: As a confident and goal-fixated striker, he often looks for a hopeful finish rather than showing more selflessness and passing to a better-placed teammate.

As well as Brazil, Gabriel Martinelli is eligible to play for Italy. Photo by DANIEL LEAL-OLIVAS/AFP via Getty Images

Gabriel Martinelli (FW; Arsenal / Brazil)

Age: 18

Estimated transfer value: €20m

The past year has been a whirlwind for Martinelli, who has gone from the lower tiers in Brazil with Ituano to starting for Arsenal in the Premier League. He was a regular in squads under Unai Emery before the Spaniard was sacked, and has continued to feature for Mikel Arteta. Playing mainly as a left-sided forward, Martinelli has scored 10 goals in 26 games in all competitions.

Strengths: Martinelli's improbable jump from Ituano to Arsenal is credit to him and the English club's scouting department. His pace, unpredictability and intensity have seen him make a real impression, but you wonder whether the energetic forward, who doesn't mind doing a shift defensively, can maintain this speed of development.

How he can improve: Still rough around the edges, he must improve his passing to reach the next level. His ability in the air also leaves a lot to be desired.

Mason Mount has six goals and four assists in the Premier League this season. Darren Walsh/Chelsea FC via Getty Images

Mason Mount (MF; Chelsea / England)

Age: 21

Estimated transfer value: €35m

After a year on loan at Dutch club Vitesse, Mount impressed last season at Derby under Frank Lampard and has since made the breakthrough at Chelsea -- he first joined the club as a 6-year-old -- after Lampard took over at Stamford Bridge. Mount has also become a regular in Gareth Southgate's England squad, scoring his first international goal against Kosovo in November.

Strengths: The busy, mobile central midfielder is never afraid to ask for the ball and thinks ahead for his next move before receiving it. Mount is creative, plays with intuition and can spot an early switch of play. He has repaid Lampard's confidence with some stunning performances and is one of the most impressive Premier League newcomers this season.

How he can improve: While he does appear very bright and full of spark early on in games, his impact can drop toward the end of the 90 minutes.

- Marcotti: Mount among Chelsea's impressive kids

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Martin Odegaard (FW; Real Sociedad, on loan from Real Madrid / Norway)

Age: 21

Estimated transfer value: €50m

It looked as if the promise that led Odegaard to earn his professional debut at 15 might go unfulfilled, but while he has not done enough to feature regularly for Real Madrid, loans in Netherlands brought valuable playing time and this season has seen him play a key role in La Real's quest for Champions League qualification. He also scored against his parent club in a surprise Copa del Rey win.

Top players under 21: League Premier League (England) 10 La Liga (Spain) 8 Bundesliga (Germany) 6 Ligue 1 (France) 5 Serie A (Italy) 5 Eredivisie (Netherlands) 1 First Division A (Belgium) 1

Strengths: The silky touch, the high football intelligence, the brilliant left foot, the ability to weight a defence-splitting pass and the elegant turns have always been in Odegaard's toolkit, but this season he has added greater consistency, end product in front of goal and maturity. Though sometimes fielded on the right wing, he is arguably more efficient as a typical No. 10.

How he can improve: To make it in Madrid, Odegaard must demonstrate more presence on the pitch and ensure the breaks between his constructive involvements become even shorter. He still appears slightly less concerned about the nuts and bolts of the game than its art and beauty.

- Hamilton, Fernandez-Abascal: Odegaard is more than a trivia answer

Victor Osimhen's club career began with Wolfsburg in Germany, before he moved to Charleroi in Belgium, then Lille in France. Maurizio Lagana/Getty Images

Victor Osimhen (FW; Lille / Nigeria)

Age: 21

Estimated transfer value: €30m

Osimhen was one of the stars of Nigeria's Under-17 World Cup triumph in 2015, when he was top scorer with 10 goals -- including the winner against Mali in the final -- and won the tournament's Silver Ball. His subsequent club form was inconsistent, but a move last year to Lille proved a catalyst; only three players have scored more than his 13 goals in Ligue 1 this season.

Strengths: Osimhen is a no-frills centre-forward, who will run and chase a lost cause knowing that his impressive pace, intense pressing and alert mind often give him the chance to make something out of nothing. At a time when many strikers want the ball to their feet, he prefers running behind defences. He is direct, sharp and clinical in his finishing.

How he can improve: At times, he is so eager to make runs behind opposing defenders that he does not even consider the option of retaining possession to allow his team to move higher up the pitch.

Christian Pulisic is one of only two Americans to score a Premier League hat trick. Getty

Christian Pulisic (FW; Chelsea / U.S.)

Age: 21

Estimated transfer value: €55m

Pulisic has been a U.S. international for four years and made more than 120 appearances for Borussia Dortmund, but in the past year has taken the next step in his career with a $70 million move to Chelsea. Early returns included a hat trick at Burnley before injury slowed his progress. The face of his national team, the Pennsylvania native remains a top prospect.

Strengths: Though he tends to look most comfortable as an inverted winger on the left, Pulisic can comfortably slot into any position behind a striker. An intelligent, modern player with excellent close control and a magnificent first touch, his low centre of gravity and ability to turn either way with the ball mean one thing: He is a nightmare to mark.

How he can improve: Very similar to other young, creative players, he mainly comes to life when he gets on the ball, giving room for improvement when he is not in possession.

- Burley: Pulisic has shown Lampard he is good enough

Declan Rice scored his first West Ham goal in a January 2019 win against Arsenal. Rob Newell - CameraSport via Getty Images

Declan Rice (MF; West Ham / England)

Age: 21

Estimated transfer value: €65m

After being released by Chelsea at 14, Rice broke through across London at West Ham, where he has played in central defence but predominantly as a midfielder. He earned international honours initially for the Republic of Ireland before switching allegiance to England in 2019, a year in which he was also nominated for the PFA Young Player of the Year award.

Strengths: In modern football, there are few disciplined, tidy defensive midfielders who enjoy mopping up loose balls and keeping things simple in possession. Rice, though, does just that, and very well; he is the kind of reliable linchpin that most teams could use. He is a dependable, efficient performer who can play with both feet and has a range of passing that keeps improving.

How he can improve: The beauty of Rice is that he just does his job. You do not necessarily want him to be more adventurous going forward or to try stuff he has not yet mastered; his role is to keep things solid, so more creative teammates can benefit.

Rodrygo made his debut for Brazil against Argentina in November 2019. Burak Akbulut/Anadolu Agency via Getty Images

Rodrygo (FW; Real Madrid / Brazil)

Age: 19

Estimated transfer value: €50m

Six months younger than his fellow countryman and Madrid teammate Vinicius Jr., Rodrygo is another young player to have followed the well-trodden path from Brazil to the Bernabeu. His early impressions have been positive for Los Blancos: Rodrygo scored within a minute after coming on for his debut in September, and then notched a Champions League hat trick six weeks later.

Strengths: If solely down to natural talent and potential, Rodrygo would be near the top of the ranked section. However, he remains a work in progress, and despite flashes of brilliance, his Real Madrid career has yet to properly take off. At his best, this is an incredibly talented forward who is probably most efficient when cutting in from the left -- he does it pretty well from the right, too -- utilising close control, technical skills and speed on the break.

How he can improve: After a promising spell in the first team at the end of 2019, he was demoted to Real Madrid Castilla. That leads to the question of whether manager Zinedine Zidane has been unimpressed with his attitude in training. Rodrygo also needs to build his upper-body strength to cope better with the European game's physicality.

Bukayo Saka was a substitute for the 2019 Europa League final at the age of 17. David Price/Arsenal FC via Getty Images

Bukayo Saka (DF; Arsenal / England)

Age: 18

Estimated transfer value: €50m

Since debuting in November 2018 for Arsenal, Saka has made a meteoric rise and this season has seen him established as a regular in the Gunners' starting lineup under Mikel Arteta. He has begun to chip in with goals, but his most consistent threat comes with the quality and precision of his crosses from the left side, which have led to nine assists in all competitions in the 2019-20 campaign.

Strengths: Already a hit at the youth level for England, Saka has become one of Arteta's most trusted performers. Reinvented as a left-back from an out-and-out winger, the pacy and tricky Saka is Arsenal's main outlet on the left, offering width and a constant option to switch play. Never short of effort, he catches the eyes with his eagerness to run at defenders and wholehearted application to defending and attacking.

How he can improve: Saka is still a learner when it comes to direct defending against an opponent and taking up the right positions. There is also work to be done on his upper-body strength -- he can get brushed off the ball too easily -- while his crossing game also needs to improve.

Boubakary Soumare's first professional club game was for Lille against Metz in November 2017. David Aliaga/MB Media/Getty Images

Boubakary Soumare (MF; Lille / France)

Age: 21

Estimated transfer value: €30m

After coming through the youth ranks at Paris Saint-Germain, Soumare opted to leave the Ligue 1 giants at 18 in order to find more playing opportunities with Lille. The move worked out for the 6-foot-2 midfielder, whose displays this season at home and in the Champions League have earned him France under-21 honours and drawn attention from clubs across Europe.

Strengths: Through his outstanding physique, agility and work ethic, Soumare has developed spatial understanding and, matched with fine tactical sense, is often well positioned to pick up second balls. He also features two good feet, from which he is able to execute a wide variety of passing.

How he can improve: Given his strength and excellent progression in possession, he could become more of a goal-scoring threat if given the license to roam.

Sandro Tonali was part of the Italy squad that reached the 2018 European Under-19 Championship final. Alessandro Sabattini/Getty Images

Sandro Tonali (MF; Brescia / Italy)

Age:

Estimated transfer value: €40m

When Andrea Pirlo says a 19-year-old is the best player in Serie A, you know you are watching a serious talent. Tonali has been a key player for Brescia for several years, but after helping his club win promotion last season he has taken his game to a new level in Italy's top flight. He is a full Italian international and will surely be snapped up by one of the big clubs very soon.

TOR-KRISTIAN KARLSEN Read all of the columns written by former scout and sporting director Tor-Kristian Karlsen.

Strengths: He combines playmaking abilities with an energetic, all-action style of play; one minute he can be organising from a deep regista role, while the next he is rolling up his sleeves to do some dirty work. Because of his club allegiance, comparisons have been drawn to Pirlo, but while there are similarities, Tonali is more of a grinder. What they have in common, however, is an excellent right foot, with which they can pick a pinpoint forward pass, almost without looking.

How he can improve: One criticism is that he sometimes tries too hard and, instead of letting the game settle, is prone to forcing the forward pass when more caution is needed. And though not fundamental to his position, there is room for improvement in his aerial game.

Ferran Torres collected his first winners' medal in club football when Valencia won the 2019 Copa del Rey. Silvestre Szpylma/Quality Sport Images/Getty Images

Ferran Torres (FW; Valencia / Spain)

Age: 20

Estimated transfer value: €55m

Previous Valencia youth players to reach the highest level include David Silva and Isco, and Torres might also have what it takes. He was the first player born in the 2000s to play in La Liga, and among the club records he owns is youngest Champions League goal scorer. He was part of Spain's Under-17 and Under-19 European Championship-winning teams in 2017 and 2019, respectively.

Strengths: Extraordinarily these days, Torres is a right-footed forward who prefers playing on the right wing. He is one of the best crossers in Europe, and when being doubled up by defenders, his favourite move involves evading two markers by going right between them while nutmegging one! Atypically for an easy-on-the-eye wide forward, he has the physique and size to go with delightful skills. His superb technique also means he brings first-class playmaking abilities when moving infield.

How he can improve: One scout I spoke to recently, who is a big fan, pointed out that he would like to see Torres be a bit more "aggressive" and "cynical" in his style of play.

Dayot Upamecano was named to the team of the tournament at the 2015 European Under-17 Championship. Oliver Hardt/Bongarts/Getty Images

Dayot Upamecano (DF; RB Leipzig / France)

Age: 21

Estimated transfer value: €40m

A key part of Leipzig's impressive form in the Bundesliga and Champions League, Upamecano has logged consistent displays in central defence and been linked with Europe's biggest clubs. He has played at every age group level since under-16 for France and, with the European Championship delayed by 12 months, has extra time to force his way into Didier Deschamps' plans for next summer.

Strengths: Few players stir up more debate within the scouting community than Upamecano, who emerged at Leipzig after Ibrahima Konate -- another candidate for this list -- was injured. Those defending him point to presence beyond his age, willingness to sacrifice in duels and eye-catching physical attributes, whereas those unconvinced refer to a catalogue of costly errors, a tendency to play aimless long balls and his propensity to give away unnecessary fouls.

How he can improve: With understanding of the game such an important component of the role, centre-backs peak later than those in other positions, so Upamecano has time on his side to become more consistent and less reckless.

Nicolo Zaniolo was included in a senior Italy squad before he had played in Serie A. Andrea Staccioli/LightRocket via Getty Images

Nicolo Zaniolo (MF; Roma / Italy)

Age: 20

Estimated transfer value: €50m

After moving to Roma from Inter in the summer of 2018, Zaniolo was thrust into the limelight when he made his Giallorossi debut at Real Madrid in the Champions League. His Serie A bow followed and consistently good performances resulted in a call-up to the Italian national team. Unfortunately, he tore his ACL in January, slowing his progress.

Strengths: He can seem deceptively uncoordinated and gangly at first glance, but behind the lanky appearance hides a near-complete, modern footballer. The versatile attacking midfielder with a sweet left foot has the intelligence and playmaking brain to be fielded as a trequartista -- linking midfield or attack -- as well as the smooth one-on-one skills to drive opposing full-backs dizzy from a wide-right position.

How he can improve: The immediate priority is for Zaniolo to completely recover from injury, then it is a matter of fine-tuning his physical attributes to become more explosive and resistant to heavy challenges.