Manchester United FC midfielder Antonio Valencia will miss next Thursday's UEFA Europa League round of 32 second leg against AFC Ajax at Old Trafford after being ruled out for a month with a hamstring problem.

Winger Valencia, 26, sustained the injury in the build-up to Javier Hernández's 85th-minute goal during Thursday's 2-0 first-leg victory in Amsterdam and will also sit out key Premier League fixtures against Norwich City FC and Tottenham Hotspur FC.

"He has a hamstring injury unfortunately," said United manager Sir Alex Ferguson after the match at the Amsterdam ArenA. "It will be four weeks. It's a blow to lose Valencia, but bit by bit we are getting stronger with Nani and Ashley Young coming back.

"Tom Cleverley has played a bit of football and Phil Jones has played a full game which is good for us. Chris Smalling was on the bench but will play in the return match at Old Trafford on Thursday."