not anyone good, anyway.
i'm sure it's not just nostalgia. sol campbell in his prime was easily a better defender than any of our CBs, and it's not really close. he was legitimately in the discussion for best CB in the world. he had the power to plow any of them over, the pace to keep up with any striker in the world, and a true defender's mentality and reading of the game. he wasn't as good on the ball as vermaelen or koscielny but who gives a shit. he got the ball to vieira and pires quickly enough. besides, he had toure next to him, who was more comfortable (when he wasn't making aimless long passes).
anyway, i agree mertesacker complements our other CB better. i'm just saying he's not a panacea - he's got his weaknesses, too, and they will be exposed.