Manchester United winger Antonio Valencia faces a month on the sidelines after picking up a hamstring injury in Thursday's 2-0 Europa League win against Ajax Amsterdam.
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 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."
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