Manchester United winger Antonio Valencia faces a month on the sidelines after picking up a hamstring injury in Thursday\'s 2-0 win over Ajax Amsterdam in the UEFA Europa League. The Ecuadorian was hurt while helping to create the second goal at the Amsterdam Arena which was scored by Javier Hernandez. \"He has a hamstring injury unfortunately. It will be four weeks,\" said United manager Sir Alex Ferguson. \"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 tonight 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 next Thursday.\"