He told The Sun: “I want John to reach the same level as Paolo, who I played with at AC Milan.
“He has been at the very top level for 20 years and John is capable of doing the same.
“I cross my fingers that he can get over this injury and go on to become the best defender in the world. I think he can do it.
“He can really be the image of Chelsea, making new players understand the spirit of the club and the story of where it has come from.”