Teofimo Lopez Jr. puts on a Joe Burrow jersey after defeating Richard Commey at MSG in December, similar to when Lopez sported a Kyler Murray jersey in his win the previous December. (0:52)

There are thousands of professional boxers in the world. Some are internationally known and heralded while others are just getting their first professional bouts under their belts. The very best stand out among the weight classes and hold their titles high, and the elite of the elite are given pound-for-pound status.

Who are the best fighters at every age? ESPN's Dan Rafael and Steve Kim have compiled a list of boxers who stand out from the masses.

To see the best fighters from 31 to 40-plus click here.

20: Joseph Adorno (14-0, 12 KOs)

Because most fighters at age 20 are still boxing in the amateur ranks, there aren't a ton of standouts. But Joseph Adorno, a junior lightweight who turned pro in December 2016, is one of boxing's top prospects. He has power in both hands, but his left hook is his best punch -- one that has drawn comparisons to the money punch of Puerto Rican legend Miguel Cotto. Adorno has not faced any serious opposition yet, but he appears to have the tools necessary to become a quality professional. Promoter Top Rank says it plans to give him a bigger push and step up his opposition in 2020.

Other notable boxers who are 20: Aaron McKenna.

21: Devin Haney (24-0, 15 KOs)

Haney, who was only 17 when he turned pro in 2015, fought his early bouts in Mexico before he was able to be licensed in the United States. But he was a prodigy, gaining a reputation for his all-around game while he was still a teenager and sparred with fighters such as Floyd Mayweather, Shawn Porter, Zab Judah, Amir Khan, Jessie Vargas and Gervonta Davis.

Haney is a dynamic fighter who turned 21 in November. He was supposed to be tested by Antonio Moran in May, but Haney dominated and scored the 2019 knockout of the year in the seventh round. Then Haney won an interim lightweight world title by hammering Zaur Abdullaev in four one-sided rounds, before being elevated to a full world titlist and making his first defense by shutout decision over Alfredo Santiago in November. Haney, who likely will move up to junior welterweight in 2020, injured his shoulder against Santiago and required surgery, so he will be out for a bit recovering. When Haney is once again healthy, he has the potential to be a top pound-for-pound player.

Other notable boxers who are 21: Vergil Ortiz Jr., Ryan Garcia.

22: Teofimo Lopez Jr. (15-0, 12 KOs)

play 8:48 Lopez: Loma is too small to handle my power Teofimo Lopez says he won't allow a natural featherweight in Vasiliy Lomachenko defeat him come fight time.

There are few, if any, young fighters in boxing as electrifying and explosive as the Brooklyn-born Lopez, a 2016 Olympian for his parents' birth country of Honduras. The 2018 prospect of the year is now a newly minted lightweight world titleholder.

Lopez has it all -- speed, power, skills, an exciting style and charisma -- to become a dominant force inside the ring and outside of it as well, as long as he can keep the inevitable distractions to a minimum.

On his way to a title, Lopez destroyed reputable opponents such as William Silva, Mason Menard, former world title challenger Diego Magdaleno and Edis Tatli via eye-catching knockouts. On Dec. 14, Lopez delivered another booming KO when he crushed Richard Commey in the second round to take his lightweight belt and set up a likely spring title unification bout with pound-for-pound king Vasiliy Lomachenko.

Other notable boxers who are 22: Shakur Stevenson, Daniel Dubois, Brandon Figueroa.

23: David Benavidez (22-0, 19 KOs)

Benavidez, who turned 23 on Dec. 17, is a two-fisted puncher with youth, size, power and the chin to become a staple of major fights for years to come. He's the kind of fighter who is happy to stand and slug if that is what it takes to win.

At age 20 in September 2017, Benavidez won a vacant super middleweight world title to become the youngest fighter ever to win a 168-pound belt. He didn't lose it in the ring, but was stripped and suspended following a positive drug test for cocaine. He seems to have learned his lesson from that transgression, showing humility and taking responsibility for his actions. He reclaimed the belt in September with a punishing ninth-round stoppage of Anthony Dirrell. Benavidez, the younger brother of former welterweight world title challenger Jose Benavidez Jr., is supposed to be back in the ring in March or April for a mandatory defense against Avni Yildirim.

Other notable boxers who are 23: Jaime Munguia, Takuma Inoue, Elwin Soto.

24: Emanuel Navarrete (30-1, 26 KOs)

play 0:44 Navarrete wins junior featherweight title Emanuel Navarrete lands a lot of hard punches, swelling Isaac Dogboe's face, and scores an upset unanimous decision to take his 122-pound world title.

Navarrete has emerged as the latest exciting and talented fighter from Mexico, in large part because of his active schedule, which included five junior featherweight world title bouts in 12 months between December 2018 and 2019 -- and four in seven months. Navarrete won a 122-pound world title by unanimous decision over Isaac Dogboe in an upset and has thus far made four defenses -- against Dogboe in a rematch and three against lesser-known opponents, most recently by fourth-round knockout of Francisco Horta on Dec. 7 in a Mexican homecoming bout.

Although Navarrete's next fight is not set yet, Top Rank hopes to keep him busy again in 2020, and also hopes to secure him a unification fight. He could be back as soon as February.

Other notable boxers who are 24: Kosei Tanaka, Erickson Lubin, Julio Cesar Martinez.

25: Gervonta "Tank" Davis (22-0, 21 KOs)

Although Davis has had legal issues outside the ring and problems making weight, there is no denying his immense talent. Davis is a crowd-pleasing action fighter and strong puncher with both hands, but the southpaw's most devastating shot is a straight left that has ended many fights. He's already won three world titles in two divisions -- junior lightweight and lightweight -- though his first junior lightweight reign ended when he was stripped for missing weight for a defense. On Dec. 28, he officially moved up to lightweight, and despite issues making weight, he did make 135 pounds and punished Yuriorkis Gamboa before stopping him in the 12th round to claim a vacant secondary title.

Davis is also a ticket-seller like few other Americans and his handlers plan to break him into pay-per-view in 2020, probably in a very attractive fight with Leo Santa Cruz. Davis has drawn strong crowds in London; Carson, California; hometown Baltimore; and Atlanta. If he can stay focused on training and conditioning -- and keep out of trouble -- he has a chance to be a major star.

Other notable boxers who are 25: Xu Can, Luis Nery.

26: Naoya Inoue (19-0, 16 KOs)

The Japanese star is an all-around talent who stands among the best pound-for-pound fighters in the world. He has power, speed and technical ability, and he has become a draw. Inoue has won world titles in three divisions -- junior flyweight, junior bantamweight and bantamweight -- and done so mostly with ease. As highly regarded as he has been for the past few years, he really broke out in 2018 and 2019 during his time in the World Boxing Super Series bantamweight tournament, where he smashed Juan Carlos Payano in one round to win a secondary title, crushed Emmanuel Rodriguez in the second round to win another belt, and then fought through a damaged orbital bone and a broken nose in the final to turn back a stiff challenge from future Hall of Famer Nonito Donaire and unify belts on Nov. 7 in the 2019 fight of the year. Following the tournament victory, Inoue announced he had signed a co-promotional deal with Top Rank that will bring him to the United States to fight regularly, beginning with his anticipated return in the spring.

Other notable boxers who are 26: Ivan Baranchyk, Murat Gassiev, Jack Catterall.

27: Jose Ramirez (25-0, 17 KOs)

play 0:49 Ramirez beats Zepeda by majority decision Jose Ramirez improves to 24-0 by defeating Jose Zepeda by majority decision and retains the WBC junior welterweight title.

Since he turned pro following his stint on the 2012 U.S. Olympic team, few fighters have improved more dramatically than Ramirez. He's a tireless worker in the gym who has also made a name for himself outside the ring, thanks to the tireless work he does for his community in Avenal and the Fresno area of California's Central Valley, where he has become a major attraction. Ramirez, who carries a devastating left hook, impressively won a vacant junior welterweight world title by decision over Amir Imam in 2018 and has so far made three defenses, all against quality opponents: a one-sided decision over longtime contender Antonio Orozco, a closer call against Jose Zepeda and a sixth-round knockout of Maurice Hooker in a signature win to unify two 140-pound belts in July.

While Ramirez hopes for an eventual unification with Josh Taylor, he will first head overseas to Haikou, China, for a Feb. 1 ESPN date with mandatory challenger and former titlist Viktor Postol. Further down the road, Ramirez could loom as a challenger for welterweight titlist Terence Crawford.

Other notable boxers who are 27: Caleb Plant, Joseph Parker.

28: Miguel Berchelt (37-1, 33 KOs)

play 0:42 Berchelt's vicious body shot forces Sosa to a knee Miguel Berchelt rocks Jason Sosa with a massive body shot to send Sosa to a knee. For more Top Rank Boxing action, sign up for ESPN+: http://plus.espn.com/.

Mexico's Berchelt has emerged as one of boxing's best and most entertaining fighters over the past few years. He won a junior lightweight world title in exciting fashion in January 2017 when he stopped Francisco Vargas in the 11th round of a competitive fight. Six successful defenses have followed, including a wide decision over former titlist Takashi Miura, another stoppage of Vargas in a rematch, and knockouts of former featherweight titlist Jonathan Victor Barros, longtime contender Miguel Roman and former secondary junior lightweight titleholder Jason Sosa in his most recent appearance in November.

Berchelt is anxious for a major fight. He has spoken often about his desire to either move up to challenge lightweight world champion Vasiliy Lomachenko (or have him come down to challenge for his belt), but his big fight will come in the form of undefeated mandatory challenger and former featherweight titlist Oscar Valdez, probably in his next fight in the early spring. That pairing looms as one of Top Rank's most attractive bouts in the first part of 2020.

Other notable boxers who are 28: Kenshiro Teraji, Gilberto "Zurdo" Ramirez, Michael Conlan.

29: Canelo Alvarez (53-1-2, 36 KOs)

Age 29 is easily boxing's most loaded. It's probably 10 deep in elite fighters, but Alvarez is, to many, not only boxing's biggest star but also my pound-for-pound king and my 2019 fighter of the year. He is already one of Mexico's best ever and has won world titles in four divisions, from junior middleweight to light heavyweight. His tremendous resume includes wins over Sergey Kovalev, Daniel Jacobs, Gennady Golovkin, Julio Cesar Chavez Jr., Amir Khan, Miguel Cotto, Erislandy Lara, Austin Trout and Shane Mosley. His lone loss came in one of the most lucrative fights in history against Floyd Mayweather.

In addition to his in-ring prowess, Alvarez is boxing's highest-paid fighter thanks to the five-year, 11-fight, $365 million contract he is three fights into with DAZN to leave pay-per-view. It was a record deal for an athlete at the time he signed it in late 2018.

Alvarez recently gave up the light heavyweight belt he won by knocking out Kovalev in November, but he is still the middleweight world champion and also holds a secondary super middleweight belt, which is the one many expect he will defend when he returns to the ring for Cinco de Mayo weekend in May.

Other notable boxers who are 29: Errol Spence Jr., Dmitry Bivol, Josh Taylor, Callum Smith, Juan Francisco Estrada.

30: Anthony Joshua (23-1, 21 KOs)

play 1:01 Atlas: Joshua was efficient to win rematch vs. Ruiz Teddy Atlas breaks down Anthony Joshua's one-sided victory vs. Andy Ruiz Jr., saying that Joshua protected his chin and was efficient.

If Alvarez is not the biggest star in boxing, it's Joshua, whose fights have drawn massive crowds to stadiums in the United Kingdom and a temporary one constructed in Saudi Arabia for his rematch with Andy Ruiz Jr. on Dec. 7. Joshua easily outpointed Ruiz in their sequel to reclaim the three major heavyweight title belts he stunningly lost to Ruiz by seventh-round knockout on June 1 in New York.

Joshua's victory over Ruiz put him back on track and added Ruiz's name to a resume that also includes excellent wins over Wladimir Klitschko in the 2017 fight of the year, Joseph Parker to unify two belts, Alexander Povetkin, Dominic Breazeale and Dillian Whyte.

After two fights with Ruiz in 2019, Joshua's 2020 looks like it will be a year of mandatory defenses against worthy opponents in Kubrat Pulev and Oleksandr Usyk. With titlist Deontay Wilder and lineal champion Tyson Fury tied up with each other probably for two fights in 2020, a fight between Joshua and Wilder or Fury appears a long way off.

Other notable boxers who are 30: Regis Prograis, Kazuto Ioka, Sergey Lipinets, Maurice Hooker.