Mourinho said of the German World Cup-winner: "Yes, he is staying. He is going to (be included on) the Europa League list because we opened spaces with Memphisand leaving and we don't have many players, and we don't have many options in midfield.
"Ninety minutes (against Wigan) was probably too hard for him, from minutes 65-70 it was hard for him but now I think he is happy.
"He was a good professional when he was not playing, and after having some minutes he will be the same. With so many competitions and games he will be an option."
Mourinho deflected a question about England captain Rooney in his post-match press conference by speaking about former England international Young.
He said: "The only player that I am aware of a possibility to leave, and I am waiting for January 31 to know what is going on, is Ashley Young, a player I would love to keep.
"I am not happy if he leaves, but he is the only player that I am informed has a possibility of leaving. That is why he didn't play and I gave chances to other people, because I don't know if he is going to stay.
"If I could choose, definitely yes he would stay with us."