It depends entirely on who else is in the side on any given day.
His best position is centre half. However, I do think that Shackell and Wharton should be the central pairing now - Shackell because of his vast top flight experience and Wharton because he is not only a very good player, but also left-sided.
Added to which, I feel our central midfield pairing from Saturday is not great - I appreciate that O'Connor and Frecklington played together successfully at Rotherham, but they really do lack pace. That will invite opposing forwards onto the defence too often, leaving them with a lot to do. Bostwick is a blocker, an old-fashioned stopper who can prevent that happening if played just in front of the defence. In other words, the job that Woodyard used to do.
That was a very slow central four we had out on Saturday (Frecklington/O'Connor, Bostwick/Shackell) with an average age of 32 - I was worried about it before kick-off. It may leave us exposed against quicker forwards.