Manchester United midfielder Park Ji-Sung has been ruled out for four weeks after suffering a hamstring injury on Friday.
The South Korea international, only recently back from a month-long stint at the Asian Cup in Qatar, damaged the muscle in training.
United manager Sir Alex Ferguson told the club's official website, www.manutd.com: "We got a blow on Saturday morning with the news that Park Ji-sung did his hamstring on Friday afternoon in training."
He added: "It was very unfortunate because it was his last kick of the ball in training as well.
"We were really looking forward to having him back after being away for a month at the Asian Cup. He'll be out for up to a month, which is a blow to us."
Park, who retired from international football after the Asian Cup, has been a vital player for Ferguson this season with United having to seek alternatives in wide positions after Antonio Valencia broke his ankle and suffered ligament damage against Rangers in September.
Valencia rejoined training over the weekend and Ferguson is hoping the Ecuadorian can play a part for the Barclays Premier League leaders over the closing stages of the season.
He added: "The good news is that Valencia started training with the reserves on Saturday.
"So he's on his way back and that will be a real boost to have him available for the run-in."