Mourinho says it's time for the Belgian to step things up.
"I think that the kid has a lot of talent, as everybody knows," says the Portuguese.
"But he has to transform his great talent into great numbers: how many goals, how many assists, how many winning goals, how many goals in big matches. Football is about numbers in a very pragmatic way. I'm ready to help him and he must be ready, too.
"He has to listen. I always say to these creative players that, if you have more than the others, you have to do more than the others. If you have this ability, you have to use this ability.
"If you do that with one objective - to score goals, or to create goals - do it. If you lose the ball, then no problem, because you had a good objective in your mind: you want to score goals or produce goals.
"[But] when you do this for fun, when you do this in midfield, lose the ball, don't defend and the team concede a goal, that's a problem. But I never tell these players, 'You cannot do this, you cannot do that'. You can do anything because you have more talent than the others, so go for it. But go to score, go to produce, not to have fun or humiliate the opponent, or put the ball through his legs. Football is not this. Football is being respectful and having objectives."