Just because Varane is a freakishly good talent who seems to have developed early, doesn't mean everyone needs to peak before their 25th birthday. Mangala had a good reputation before joining City, and has shown flashes of brilliance alongside some mediocre moments. He'll come good. When I think of it, France has an incredibly strong set of centrebacks, and a good set of upcoming centrebacks (e.g. Zouma, Laporte etc).