Mourinho thinks playing in Spain for two years as a loanee for Granada and Valencia has helped.
"I wasn't happy that he didn't play in his best position for Valencia," he said. "But from a human point of view, I think it was a great experience. He became more of a man, more ready physically and mentally.
"Then it was the question in the Premier League to play him in the position we think is the best, to educate him, to help him understand the position.
"The fact that we had only three midfield players for the pre-season, he had to play all the five matches for 90 minutes which was very good for him."