Carrick is played differently for United though, when he's allowed to sit back and dictate play he's one of the best in the league at doing so. But more often than not SAF has him and Fletcher as the water carriers, which he isn't at all.
Part of his drop in form is to do with Ronaldo leaving, with Ronaldo teams had to double up on him and Rooney which left fucktonnes of space for Carrick to exploit, which he did briliantly. Now because teams press United more as there is less to worry about, so to speak, he hasn't the time to dictate play and is often found playing like Petrov and keeping it simple and boring.
He's head and shoulders above Petrov, but never really gets a look in for England because he's a luxury midfielder.