Manchester United have been rocked by an injury to midfielder Kobbie Mainoo, who faces weeks on the sidelines with a muscle problem.

The 19-year-old was forced off in the home defeat against Tottenham and while he missed the subsequent Europa League trip he allayed fears over his fitness by returning to the side to face Villa.

But after being brought off with discomfort in his hamstring at Villa Park – forcing him to pull out of Lee Carsley’s England squad – further tests have determined that Mainoo faces ‘a few weeks’ on the sidelines in a major blow to under-fire boss Erik ten Hag.

Mainoo is a regular starter under the Dutchman and has been his preferred central midfielder with fitness and form concerns around Mason Mount and Manuel Ugarte, who undertook a recovery training session away from the main group on Thursday after returning from international duty.

Mainoo has started every Premier League game this season and so his absence will force Ten Hag, who will address the injury in front of the media on Friday, into a reshuffle this weekend for the visit by Brentford.

Kobbie Mainoo is facing a spell on the sidelines for a number of weeks after picking up a knock versus Tottenham

Erik ten Hag will be disappointed to go without his midfielder as he prepares to face Brentford

In more reassuring news summer signing Noussair Mazraoui has returned to training this week

In better news, United confirmed that full-back Noussair Mazraoui was fit enough to train on Thursday.

Mazraoui, who came off ill in the draw against Villa, underwent a heart procedure recently after complaining of palpitations.

Club sources allayed fears by detailing that it was a minor corrective procedure and Mazraoui himself further eased concerns by taking part in Thursday’s training session.

Alejandro Garnacho and Amad Diallo also trained after missing games for Argentina and Ivory Coast respectively during the international break.

Mount, who is recovering from a knock picked up against Tottenham, is making progress, while Luke Shaw, a long-term absentee, is stepping up his return. Both remain huge doubts for Brentford this weekend.