Manchester United midfielder Shinji Kagawa suffered a knee injury during his side's clash with Sporting Braga in the Champions League on Tuesday.
The 23-year-old picked up the injury during the first half of the Red Devils' 3-2 victory at Old Trafford and was replaced by winger Nani at half-time.
"Shinji twisted his knee," manager Sir Alex Ferguson told United's official website. "We had to take him off. He struggled on for 20 minutes after he got the injury.
"We'll assess it in the morning as it's too early to say what the damage is."
Kagawa joined United from German champions Borussia Dortmund in the summer.
