Amsterdam, Netherlands – Manchester United winger Antonio 0 Europa League win at Ajax, and will be sidelined four weeks.
The 26-year-old Ecuadorian was injured as he set up the second goal for Javier Hernandez. Valencia only entered the match as a second-half substitute.
"He has a hamstring injury unfortunately. It will be four weeks," United coach Sir Alex Ferguson said. "It's a blow to lose Valencia tonight, but bit by bit, we are getting stronger with Nani and Ashley Young coming back."
Young scored the other goal for United, which takes the two-goal lead back to Old Trafford for the second leg next Thursday.