Ten Hag added the injury to Martinez - who only returned from a long-term foot injury last month - is a "personal disaster" for the defender.

Martinez suffered the issue when tangling with Vladimir Coufal as he attempted to shield the ball out for a goal-kick in the second half at Old Trafford and was replaced shortly afterwards.

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Asked how serious the Argentina international's issue is, Ten Hag said: "I can't say but it doesn't look good. There is a bad concern.

"We have to wait for a few days for the diagnosis. We do everything to get the right diagnosis and see what is the damage.

"He is very sad, very disappointed. We all feel really with him. First of all, it is a personal disaster when it is really bad, but also for the team it is really bad because he definitely brings us a lot."

Speaking to Sky Sports, the United boss added: "It is very bad - very bad for him, very bad for the team. He is a very important player for us.

"We have centre-backs who can fill in but he brings spirit to the team, apart from his football abilities."

Martinez spent nearly three months on the sidelines before returning for the 2-2 draw with Tottenham on January 14.

Since he was brought back into the side, United have remained unbeaten, winning three and drawing one of their four games.

However, they have actually won more points and conceded fewer goals per match without Martinez in the side in the Premier League this season.

United are well-stocked at centre-back should Martinez remain absent in the long term, with Ten Hag able to call on Raphael Varane, Harry Maguire, Jonny Evans and Victor Lindelof, who returned to the squad after injury on Sunday.

Man Utd's next five games

• Aston Villa (A) - Premier League, Sunday February 11, live on Sky Sports
• Luton (A) - Premier League, Sunday February 11, live on Sky Sports
• Fulham (H) - Premier League, Saturday February 24
• Bristol City/Nottingham Forest (A) - FA Cup, Wednesday February 28
• Manchester City (A) - Premier League, Sunday March 3, live on Sky Sports

Moyes: Martinez made a 'huge difference'

West Ham boss David Moyes said Martinez made "a huge difference" for United, explaining: "He brings much greater calmness on the ball in their build-up play.

"I am not an expert on Manchester United but I think that makes them look more comfortable."

Moyes even highlighted a key moment in the game when Emerson was running through on the angle after dispossessing Harry Maguire.

Martinez was able to force Emerson wide, with Moyes saying: "I think he was a bit spooked by Martinez."

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