Manchester United boss Jose Mourinho insists Antonio Valencia has been missing due to injury.

Ashley Young has taken Valencia's place in the starting XI, also skippering the side in his absence.

But Mourinho has told reporters that surgery is the real reason behind his unavailability.

"The reason was that he was 10 days without training with a problem," Mourinho said at his pre-match Champions League press conference.

"Not an injury but a problem that he had a very complicated surgery on his mouth. And 10 days without training needed a little bit of time to recover some level after that."