If Modric cannot objectively consider that he has as good a chance at winning something as part of this Spurs squad as he would any where else, then he is an idiot, and I really don't think he is an idiot. Misguided, perhaps, but he seems to have been put right. If he goes to United, he will be nothing more than a bit-player, just like Berbatov. If he goes to Chelsea, I really cannot see him doing as well, as they play far too narrow, and he seems like a player who likes to work the spaces. There is no guarantee that, should he move to another club, he'll be nothing more than an average player at best, or a flop at worst.
