Mancini said: "I have spoken to Mario, two weeks ago. I said, 'Please, we have 13 games to play and the Europa League too - try to have good behaviour on the pitch and think only of playing football.
"I think if his head is okay in the next two months, he will be an important player.
"It's difficult to find a good definition for him. We know that Mario is a fantastic player. He's young, sometimes he will do some mistakes but, for this reason, if he can keep his composure for the next months, he will be an important player for us, in the Europa League and the Premier League."