Fingers will be crossed for five United players ahead of Tuesday's trip to face AS Roma in the Champions League.
Michael Carrick, Patrice Evra and Rio Ferdinand were all withdrawn in a triple substitution during Saturday's 4-0 win over Aston Villa. United then played the last five minutes with ten men after Ryan Giggs also left the field.
"I had to make the changes because of injuries," said Sir Alex Ferguson.
"Carrick, Rio and Patrice Evra all had injuries and then Giggs got injured towards the end. With the rain continually coming down, the pitch was starting to prove very heavy and that can be a problem with hamstrings. Hopefully they'll be all right (for Rome)."
The fifth player causing fresh concern for the manager is Edwin van der Sar. The Dutchman missed the Villa match, leaving Tomasz Kuszczak to start in goal with Ben Foster - who is ineligible for Europe - on the bench.
"Edwin van der Sar may be a doubt for Tuesday," admitted Sir Alex.
"He’s got a groin problem again, it’s happened two or three times in the last few weeks. We'll see how he is over the next few days. Not risking him today gives us a better chance."