Manchester United have announced winger Antonio Valencia will be out of action for up to a month due to a hamstring injury sustained against Ajax.
Valencia was brought on in the second-half for Ashley Young and then departed for Danny Welbeck within ten minutes after appearing to tweak his hamstring.
''He has a hamstring injury unfortunately,'' Ferguson said after the game. ''It will be four weeks. It is a bad blow for us."
United do have a plethora of options on the wing with Young, Nani, Park Ji-Sung and Ryan Giggs all able to fill in, but Valencia's form has been impressive of late and his absence will be felt as the Red Devils try to close the gap on rivals City at the top of the Premier League.
If there was a positive from Valencia's injury, which will rule him out of the key Premier League showdown with Tottenham at White Hart Lane on March 4, it was that Nani and Young were amongst those to return to action.
Young marked his first appearance since Christmas with his fourth goal of the season, breaking the deadlock after a dismal first-half display.
''It was Ashley's first game in two months,'' said Ferguson. ''Nani came back as well, Phil Jones has played a full game, which is good for us and Tom Cleverley has played a bit of football too so bit by bit we are getting stronger.''