The Belgium midfielder celebrates his 20th birthday with an impressive 39 Premier League appearances under his belt already, but can he push on and become a Manchester United legend?

Adnan Januzaj at 20: will he be the next Giggs or the new Macheda?

Adnan Januzaj awoke on Thursday to his 20th birthday, though any celebrations may have been tempered with doubt when contemplating his Manchester United future.

The cloud over the potentially sparkling years ahead that seemed apparent during last season’s breakthrough under David Moyes is the present. Now, Louis van Gaal is in charge and the club have splurged £150m-plus on a new galáctico policy that recruited Radamel Falcao and Ángel di María in the summer. With Januzaj viewed as a striker, a No10 or a winger, this means he has yet more competition for regular football – alongside Wayne Rooney, Robin van Persie, James Wilson, Antonio Valencia and Ashley Young – under a manager showing only limited faith in him.

Januzaj’s emergence during Moyes’s doomed tenure billed him as a sure-fire bet to enjoy many dazzling days in United livery. This hope has faltered somewhat under Van Gaal, whose demand for consistency after Saturday’s win over Leicester City explained why it was only a sixth league start this term for the Belgian.

Januzaj said: “Last year I played a lot of games and every week I was feeling better and better. I’ve not been playing a lot this year but it’s OK. I will try to work hard in training and out on the pitch.”

In the same interview, given to United Review before Tuesday’s FA Cup win against Cambridge United, Januzaj also said that the systems used by Van Gaal “really can make it more difficult for me to play”. No reading between these lines is required to find the frustration of a footballer, who can claim to be United’s most talented, at being shunted to the fringes by the Dutchman. At the same juncture of the last campaign Januzaj had made 10 Premier League starts.

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Yet in the Premier League era only Giggs, whose No11 shirt Januzaj inherited, and Cristiano Ronaldo had made more United league appearances by their 20th birthday. Giggs, whose debut came at 17, accumulated 56 games (a total of 4,579 minutes), scoring 12 times and making nine assists.

Ronaldo, whose first match was at 18, totalled 3,127 minutes from 51 appearances, with eight goals and seven assists.

Januzaj, 18 on his first league start in last season’s 2-1 victory at Sunderland when he scored both United goals, has now made 39 appearances, of which 20 have been starts. In his 2,165 minutes on the pitch, he has added two more goals and has three assists.

In this context Januzaj can be proud and should be optimistic about how high his United career might fly, especially when viewing the name underneath him on the list of appearances before their 20th birthday – Rooney.

Now the captain, Rooney made his debut a month before his 19th birthday and by 20 had featured in 38 matches – one fewer than the Belgian – though his 2,923 minutes is markedly greater than Januzaj’s tally, as are the Liverpudlian’s 15 goals, the best by any United teenager since the rebranding of the old First Division. Rooney’s numbers, of course, are even more impressive as he has played 67 league games, with 15 goals, for Everton.

Giggs, Ronaldo and Rooney are undoubted success stories: teenagers who carried on developing their potential to mature into bona fide stellar players. Yet the roll call of United teenagers playing in the league is long: 44 since the 1992-93 season. The list includes names such as Anderson, Federico Macheda and Terry Cooke, who act as a warning to Januzaj of how Old Trafford careers can fade for disparate reasons.

Anderson – 22 games, 1,388 minutes, two goals, one assist – finally left on a free transfer to Internacional this week. With many United fans pondering how he remained at the club for eight years despite fitness and dedication problems, the midfielder’s failure can be filed under “wasted potential”.

Macheda – 16 games, 533 minutes, four goals, two assists – also left on a free transfer, for Cardiff City last May, having been loaned to five clubs. After bursting on to the scene towards the end of the 2008-09 campaign, with vital goals against Aston Villa and Sunderland that helped claim the title, the Italian’s problem was being unable to find a second act.

Cooke – four appearances, 117 minutes, no goals and a single assist – was the Class of ’92 member who hung around too long. Five years after his debut, the winger finally left United for a peripatetic career, his CV showing 11 differing clubs of which Azerbaijan’s Gabala was the last, in 2011.

Januzaj’s talent may appear on a higher plane than any of these names, yet at 20 Anderson was a former Golden Ball and Golden Boy recipient, a Brazil international and a Premier League and Champions League winner. The challenge for Januzaj is to show more backbone than Anderson, to prove Van Gaal’s reservations are wrong with fine performances whenever he plays.

He can still flit in and out of games. This is what causes Van Gaal’s hesitation in naming him each week in the XI. At 20, now is the time for Januzaj to grow up.