Might sound weird since City have lots of great players but for me he carries City. If he has a good game, City will win. When he's off, the usually get dumped out of the CL.
For me personally the first tactic I'd play against City is to Park Ji Sung KDB. Forget if it frees up space elsewhere, you're still coming up ahead.
100% the guy is a monster of a player and city are very lucky to have him.