The former Italy and Brazil international believes the France international will kick on, but has questioned his development in recent times.
Former Juventus attacker Jose Altafini feels new Manchester United signing Paul Pogba has not made any progress over the past two seasons.
The France international signed a five-year deal with United on Monday to return to Old Trafford for an initial transfer fee of 105 million euros ($117M) after a four-year spell with Juventus.
He had developed into a key figure at Juventus and won four Serie A titles, two Coppa Italia and as many Supercoppa Italiana.