Erik ten Hag provided an update on Lisandro Martinez's injury after the defender limped off mid-way through the second half against West Ham.
On Sunday Rasmus Hojlund and Alejandro Garnacho provided the goals as United claimed a resounding 3-0 win over West Ham - the club's biggest home league victory of the season.
Hojlund, who was celebrating his 21st birthday, netted his fourth goal in as many games in the 23rd minute, before Garnacho scored twice.
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It was the first time United won three successive games since October and only the second time they had managed it all season.
However the win came at a cost after Martinez, in only the fourth game since his comeback from a foot injury, appeared to injury his knee in a tangle with Vladimir Coufal.
While he tried to continue the Argentina international ultimately had to be replaced shortly afterwards.
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Ten Hag said that Martinez's injury appeared "bad" for the player and the team.
He added, speaking to the BBC: "It seems bad. We have to wait, make the right diagnosis in the coming days and then we will see. Hopefully it is not too bad, we can only pray.
"He worked so hard to return and now after two games it looks like he has to sit some games out again."
On the performance as a whole however, Ten Hag said: "I said before, when you don't build on the last win then it is nothing. That was our challenge before and the lads did it.
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"I am happy with the way we played. We were a threat all the game through. When we serve our front line we can score goals. They can be direct and score goals.
"The future for Manchester United is very good because we have high potentials. I think that picture [below] covers the lot, how they are together and want to play football with adventure and enjoyment. If we keep this process going I am sure we will achieve high levels.
"We are building a team, we signed young players and give them opportunities. This is a process with ups and downs and we have to realise this. Our experienced players will help them and we need them and they will help the young players perform."
Topics: Lisandro Martinez, Manchester United, Erik Ten Hag, Premier League