Manchester United manager Sir Alex Ferguson has confirmed that Shinji Kagawa will be out for as long as a month with a knee injury.
Japan international Kagawa picked up the injury midway through the first half of the 3-2 win over Braga in the Champions League in midweek, but he played on for a further 20 minutes before he was eventually withdrawn at half-time.
The attacking midfielder is now set to miss as many as seven games for the club, including Sunday's trip to face Premier League leaders Chelsea, the home league clash against Arsenal and two further European games.
Ferguson said in his pre-match press conference ahead of the Chelsea trip: "It's a knee injury similar to the one Ashley Young had but not as bad.
"I think playing on with the injury did not help the situation for him, even though he did well to play on with it. It's disappointing for him."
Kagawa, 23, has played six of United's eight Premier League games so far this season since joining the club from Borussia Dortmund in the summer, during which time he has scored twice for the Old Trafford club.
Sunday's game against Chelsea is the first of two in a week for United as they return to Stamford Bridge on Wednesday for a Capital One Cup tie.
There was better news for United in defence, with Ferguson reporting that long-term absentees Chris Smalling and Phil Hones are both close to returning.
Smaling is back in training having been ruled out since the end of last season with a broken metatarsal, while Jones is also yet to feature this term due to a knee injury.
"(Smalling's return) is a big bonus for us," Ferguson said.
"Phil Jones should start (training) a week on Monday as well."