Mourinho left Rooney out of his starting line-up against Leicester on Saturday lunchtime and saw his side produce their best performance of the season.
Rooney was restricted to just a seven minute outing at the end but Mourinho is adamant that the 30-year-old still has plenty to offer.
“He’s a big player for me, a big player for United and a big player for this country,” said the Portuguese.
“I have nothing else to say. He’s my man, I trust him completely and he is happy at this moment.
“His team won, his United won, that’s normal.”
The emphatic win over Leicester was United’s first in three games, and Mourinho was delighted with the display.
“It was a very good performance,” he said. “It’s obviously a very good result, it’s not easy to win against them and even more difficult to win in such a comfortable way.
“I think the team played very well, you score four goals, and the striker doesn’t score a goal and I think the striker plays phenomenal.
“Ibra [Zlatan Ibrahimovic] played absolutely incredible in the way he started our pressure. My team as a team played very well.”