Manchester United striker Robin van Persie will undergo a scan this morning to determine the severity of the injury he picked up last night.
The 30-year-old Dutchman went down in the final stages of Manchester United's Champions League encounter with Olympiakos after receiving a knock to the back of his leg.
Van Persie, who scored a hat-trick against the Greek side last night to send Manchester United through to the quarter-finals of the Champions League, was replaced by Marouane Fellaini with five minutes to go.
Manchester United boss David Moyes said after the game that he thought Van Persie would not be sidelined for a substantial amount of time as it was just a minor knock.
"I don't think he is too bad," said Moyes. "He has got a knock just behind his knee.
"We will assess it and we will know more in the morning.
"He has got a knee in the back of his knee but hopefully it is not too bad."
Moyes will be hoping Van Persie will be back in action in time for Manchester United's home match against arch-rivals Manchester City next Tuesday.
Manchester United take on West Ham on Saturday - but the Dutchman is likely to be rested even if he does prove his fitness to Moyes.