Lisandro Martínez left the field in tears and Ruben Amorim said there were fears the Manchester United defender has suffered a “serious” knee injury.

The Argentine centre-half fell awkwardly after challenging Ismaïla Sarr in the 77th minute of the 2-0 home defeat by Crystal Palace and appeared in visible distress after signalling almost immediately to come off.

Concerned team-mates watched on as Martínez received six minutes of treatment on his left knee, with Manuel Ugarte crouching down to comfort the emotional defender, before he was taken off on a stretcher in tears.

“We are going to see in the next days but I think it is a serious situation,” Amorim said. “He is not only a great player but a strong character in the dressing room. He felt it and when you are a player, you know when it is something serious. We are here to help him in this difficult moment like he has helped us.

“I think it’s a bad situation, let’s wait to assess things with the doctor but I think it’s a serious situation.”

It would be Martínez’s third serious injury since his £57 million move from Ajax in July 2022. He suffered medial collateral ligament damage to his right knee a year ago that ruled him out for 3½ months after a brief, aborted comeback.

He also fractured a metatarsal towards the end of his first season and then suffered a recurrence of the problem the following September that kept him out for almost four months.

United will hope the prospect of losing Martínez for a lengthy period is tempered by the impending return of Luke Shaw, who is back in full training having last started a game for the club 12 months ago.

The club also confirmed the signing on Sunday of Denmark left wing-back Patrick Dorgu and have also signed 18-year-old centre-back Ayden Heaven from Arsenal.