The 21-year-old has relinquished the No11 jersey at Old Trafford and his future must be in considerable doubt as José Mourinho weighs up whether to retain him

The Manchester United career of Adnan Januzaj, a former heir apparent to Ryan Giggs, is now in a last chance saloon as José Mourinho assesses whether to retain the forward.

As United prepare to take on Manchester City in Beijing on Monday, Januzaj is fighting for a future at the club which once seemed so bright.

The issue is not a lack talent but the approach of the 21-year-old. His breakthrough season, when he starred under David Moyes in the ill-fated 2013-14 campaign, offered no hint of the questionable attitude that has since stunted his progress.

The view at the club among the coaching staff and in the dressing room is that Januzaj’s drift to the fringes may end in him wasting his chance at Old Trafford.

When United announced provisional shirt numbers on Thursday there was a sign of how far Januzaj has fallen.

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When Giggs retired after a supremely successful 23-season career at United in 2014 his iconic No11 jersey was given to Januzaj. At the club it was billed as passing of the baton moment. The handover was supposed to herald Januzaj becoming a first-team fixture for the foreseeable future.

Giggs, who had become Louis van Gaal’s No2, gave a special interview to the club website in which he extolled Januzaj’s virtues. Not any longer. After two seasons wearing the No11 Januzaj has quietly moved to No15, while Anthony Martial, who had to vacate No9 for the incoming Zlatan Ibrahimovic, is to wear Giggs’s former number.

Januzaj broke into the consciousness in October 2013 when Moyes handed him a first Premier League start at Sunderland. United won 2-1 and Januzaj scored both goals.

By the time Moyes’s team travelled to Chelsea the following January Januzaj was established in the XI and Mourinho, then in charge at Stamford Bridge, was saying: “He’s a fantastic player. He is not 18 – he is 25. He is so mature and comfortable. A very good and important player.

“I just think he is a very good player with the great conditions to have a great long-term career. I don’t know the boy individually but it looks like he has the lot.”

That is some praise; the kind Januzaj would welcome hearing again from the man who is now his manager. The sense, though, is that he could fade completely from the picture at United.

In Mourinho’s first game in charge, last Saturday’s 2-0 victory at Wigan Athletic, Januzaj was given the second half to impress. He failed to do so during a run-out in which the manager switched him between the right and left flanks.

In Friday’s tour opener, a 4-1 defeat to Borussia Dortmund in Shanghai, Januzaj played only the closing minutes. There were moments of sparkle as there often are in the cameos Januzaj has become used to, but the real test is his attitude on the training ground.

It is there that Januzaj has disappointed with his application and his team-mates are concerned he may not fulfil his potential. During the 2014 World Cup in Brazil with Belgium it was a similar story: those in the camp believed he had more to give. Two years later he was not selected for Euro 2016.

During Moyes’ tenure – lasting only 34 Premier League matches – Januzaj was a rare shaft of light. His form earned him a five-year deal worth around £60,000 a week in what was viewed as a coup by United.

Now Mourinho decides whether to let him go, either permanently or on loan again, following last season’s unsuccessful temporary spell at Dortmund.

That ended prematurely after Januzaj decided he wanted to return to United due to a lack of game-time. One player who kept him out of the Dortmund side was Henrikh Mkhitaryan. Earlier this month Mourinho signed the Armenia captain from the German club, in another blow to Januzaj’s prospects.

The manager is also deciding whether Bastian Schweinsteiger should be another to head for the exit door. Mourinho’s pursuit of Juventus’s Paul Pogba – or another major central midfielder – before the window closes is a threat to the German’s future. Another is that Mourinho has informed Marouane Fellaini that he wants the Belgian to stay.

By 1 September, when the transfer window closes, Januzaj and Schweinsteiger could be two of the first major casualties of the new Mourinho era.