Japan midfielder Shinji Kagawa faces an anxious wait to discover the extent of the knee injury he suffered in Manchester United's 3-2 Champions League win over Braga on Tuesday.
Kagawa twisted his knee midway through the first half at Old Trafford, but played on until half-time before being replaced by Portugal winger Nani.
United manager Sir Alex Ferguson admitted he is uncertain how severe the injury is, but he confirmed Kagawa will be checked out by the club's medical staff on Wednesday.
It would be a significant blow for Ferguson if Kagawa is ruled out for a prolonged period as the 23-year-old Kobe-born star has made a strong start to his career at United after a pre-season transfer from German champions Borussia Dortmund.
"He twisted his knee and we had to take him off at half-time," Ferguson said.
"He struggled on for 20 minutes or so after the injury. We will assess it in the morning. It is too early to say what damage, if any, there is."