No, Mikel cannot and will not be a replacement for Essien. But can he cover for him? Absolutely, though I will agree that there's scope for improvement. Some people here have mentioned that he flops during a big game. He does make mistakes, say for example when he failed to close down Sneijder in the 2nd leg of UCL in2010 in a move that led to goal. But in the leg before that at San Siro, Mikel was performing an A-game and Sneijder was nowhere in sight. Thus in Mikel's case, its not incapability but inconsistency that's a problem... Can Chelsea do better than Mikel? Maybe. But there aren't too many options out there, and considering the kind of crap that passes for a holding mid in other teams, I'd say we're lucky to have him...