Manchester United manager Jose Mourinho has explained the absence of Antonio Valencia in recent matches by saying the right back is recovering from a "very complicated" operation on his mouth.

Valencia last played for United in the 0-0 draw against Spanish club Valencia in the Champions League on Oct. 2.

Asked why Valencia had been missing, Mourinho says "the reason was that he (Valencia) was 10 days without training with a problem — not an injury but a problem that he had a very complicated surgery on his mouth."

Valencia was back in practice on Monday ahead of United's match against Juventus in the Champions League on Tuesday.