C'mon.. I'm not saying that great player is the great coach. Vialli didn't have such players and finances as Raniari had in chelsea this is the difference and when you saying that Ranieri coached many good teams you should metion that yes he coached a big teams which was winning before and after Ranieri but not with Ranieri. So he has nothing to do with good coaching and even learning something or gaining experience in his 70, in the other hand Vialli is young and he can progress
