Manchester United will be without in-form winger Antonio Valencia for up to a month after he injured his hamstring, Sir Alex Ferguson confirmed.
Valencia pulled up late on in Thursday night's 2-0 win over Ajax in the Europa League, having come on as a second half substitute and helped to set up Javier Hernández for United's second goal in the game.
The Ecuadorian, who missed the majority of last season after breaking his left ankle, has been in outstanding form in 2012, with a goal and three assists in his last four English Premier League games.
"He has a hamstring injury unfortunately," United boss Ferguson said. "It will be four weeks. It is a bad blow for us."
The injury will see Valencia likely missing for the league trips to Norwich and Tottenham followed by United's home game with West Brom on March 10.