Like I said before, realistically, this Mata deal is never going to happen. Unless there is some leverage we can use, like a contract expiring, and as far as I know Mata is bound until 2016. There is no way Chelsea will let a player of his caliber (and his market value) go without asking for an arm and a leg, and at this stage we don't have neither an arm nor a leg to spare. Nay not even a finger. They could be as generous as wanting Pogba in exchange for Mata+money, and we still wouldn't be able to say yes.
I say they would be generous offering that because while Pogba may rise in value very significantly, he is as of yet not worth as much as Mata. While most anyone can see that Pogba's market worth is probably going to rise in a meteoric fashion, right now he isn't worth as much as Mata in value. However, Pogba could conceivably be at a much greater market value in a couple of years. Giving him up would be giving up these (potential) gains. Which any good manager wouldn't ever do.
In short: We can't get Mata. It's nice to dream, but if they are going to sell him to anyone, why not squeeze 50m out of ADL or P$G instead of (relatively) poor us? The only reason would be to get a player in exchange, and we can't afford to give up any.