Ole Gunnar Solskjaer has admitted he is unsure how bad Anthony Martial's injury is but is confident the Frenchman will be available to face Wolves this week.
Forward Martial was forced off with a knock in the 77th minute of United's 2-1 victory over Waford on Saturday.
He was replaced by defender Marcos Rojo, as Solskjaer managed to win his first game as the Red Devils' permanent manager - having signed a three-year contract earlier this week.
Martial had netted the second United goal, after Marcus Rashford had bagged the opener in a close match with the Hornets.
But now, Martial is facing a race against his own fitness to be ready for United's next fixture - Tuesday night's Premier League clash against Wolves.
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When asked about the extent of the damage to Martial, Solskajer said: "I don't know.
"Hopefully he can be available for Tuesday.
"He got a bad knock. We'll check him on Monday morning, probably."
Solskjaer acknowledges that United were "sloppy" at times during the win over Watford .
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Put to Solskjaer that it was a good result but perhaps a less impressive performance, the newly-appointed manager said: "Well summarised.
"(In the) first 20 minutes we started so slow and sloppy and you could see we've had players out with injury and the international break.
"We've not been able to train them that much, so it's one of those first games after an international break that you look forward to but know there might be a potential banana skin, because Watford are a good side.
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"They didn't have that many players away and I think they deserved to take the lead.
"But after we scored, for the rest of the first half we played some great counter-attacking stuff (and) defended well.
"We had to because they were dominant but Chris (Smalling) and Jonah (Phil Jones) especially were fantastic, (they) kept us in it.
"In the second half we started sloppier but at 2-0 we were in control until they scored and then anything can happen, but three points is all you can get."
