I think this year that was down to who he was playing at the back with (i.e fry, coulson and mcnair), he's the best out of all of them considerably. RVDB played a couple of games with him too, as well as Engel, but neither of those really hit the ground running either. Also, beginning of the year we were all over the place with what was going on in front of him, had a lot of changes etc.
So, for all of that, and where we were shipping goals, it's more correlation not causation for me etc.
We were more solid at the back last year, probably even with a worse defence than what we ended up with this year. I think if you add him in there, then we will just be better all over the pitch as he's as good or better than the rest, and he is probably the best captain/ organiser when we're a settled side.