Marouane Fellaini has had surgery on his injured wrist, meaning Manchester United's £27.5m summer signing will be out for a further six weeks. Fellaini was already sidelined by a back problem that had prevented him from playing for United since the 1-0 defeat to Everton at Old Trafford on 4 December.

David Moyes had hoped the 26-year-old could return from the back issue to be available for the busy festive programme. The manager spoke last week of sending the midfielder for a further scan to determine if Fellaini should have the procedure on his wrist.

Having now done so, Fellaini will hope on his return finally to kickstart his United career after a disappointing beginning in which his form has been uneven.

The Belgian had been playing with a plaster cast on his wrist and had been in some discomfort that had been limiting his ability to play completely freely.

Moyes's decision means Fellaini should be match fit for the Champions League last-16 tie against Olympiakos, the first leg of which is in mid-February.

"He had his operation on Saturday morning," Moyes confirmed on Monday. "We just couldn't get him recovered from his back. We thought it would be okay after 10 days but it wasn't getting any better so we made a quick decision to get the wrist done. We think it will be six weeks but there is a chance it could be shorter than that."

Moyes confirmed the back injury should recover with rest and he anticipated Fellaini, who was back in Manchester on Monday, would go on to show the form which got him a summer move from Everton in the first place.

"His back problem is going to take time. That is a muscle injury which wasn't healing," said Moyes. "It is unlucky. He has not felt 100 per cent because of his wrist. He has been finding it difficult.

"I asked him to see if he could get over the Christmas period. He got the back injury against Everton and since then he has never really been right. I have no doubt he will eventually be a good player for us."