I never liked his defending even when he was at his best. I know he won a lot of tackles and all that, but he gives up too much space and has to do too many things to accomplish anything when defending.
He's not that solid, get-it-right-the-first-time midfield presence that i like and want.
Other than that he's a great player. Never gives up, loves football and has a terribly inventive mind for it, great lungs. And obviously he's plenty talented. Could do a Lampard for us if he smartens up a bit.