Distin and Stones' careers overlapped at Everton with the England defender's first two-and-a-half seasons on Merseyside coinciding with the latter part of the Frenchman's six-year spell at Goodison Park.
Distin told the Beautiful Game podcast: "I'm not sure if he has got that defensive grit. He is an amazing player with the ball, really confident with the ball but that is possibly the modern centre-back. As a modern centre-back, yes he is amazing. Did he fulfil his potential? No.
"He still has a lot to learn and he has to be a lot more consistent. Can he fit in every team? I don't think so either.
"He is perfect for Guardiola. Will he be perfect for a team who have to be stronger defensively first and then have less possession? I am not sure he is there yet.
"Definitely he has all the attributes but I feel like something didn't click for him yet.
"He could be much, much better than he is now. When I see that Manchester City would play a midfielder at centre back when they have two or three centre-backs, as a centre-back that would hurt me greatly.
"That's my job and you take a midfielder to play in my position? That would hurt me. I don't know if he doesn't have the confidence of the manager or if something else but something needs to click with him."