koscielny will be fine, but the thing with him is that his style is so uptempo and hurried that he always plays right on the edge. he's always barging in and getting in tight, which is good, and it looks mighty impressive when he plays a flawless game, but it leaves him with a small margin for error, vulnerable to a slip or other random accident, and he sometimes looks panicked.
my personal preference is for players who make the game look simple, eg a no fuss, no nonsense CB who reads the danger and just shepherds players away from goal. ideally, they'd be big bruisers with pace like sol campbell, who is basically what i picture when i think of the archetypal CB.
