Isn't it just possible that Gary had a down year? In judging whether or not the line did well and/or whether Walker is still the player he once was I'd have to factor in the play of Seth Payne who's just lately started looking like the guy he was before his knee injury.
I'm in the "let's see what this line does next season" camp on this question. Almost everyone has a down year every now and then. Next year I bet Walker is bringing the Funk like he did in 2002.