The Belgian is being linked with PSG.
But Mourinho insists: "He had a good season, an improvement. He was brought to a different level of performance and understanding of the game.
"For example, his performance at Manchester City was very complete. He's a young guy and his evolution is fine. Does he still make mistakes? Of course he does. It was the first time in his life he played a Champions League semi-final, it's a career that is only starting."