Former Juventus defender Ciro Ferrara has no doubts about the quality of Napoli stopper Kalidou Koulibaly.

However, Ferrera says the Senegal international isn't yet the best in the world.

He said, "If Koulibaly is the best defender in the world? Certainly among the first three, then it is a question of preferences.

"While before he played more as a unit, in the last year I have the feeling that he is not afraid to play man against man like he used to. Today it is important to have strong defenders who agree to play man against man.

"Koulibaly is impressive in physical strength, in recoveries but also in footwork. He made great progress, by law he is among the first three in the world."