Surely, Kerr mouthing off is a good thing? (stick with me here) We need a captain who isn't afraid to get right up there in the face of the referee, clearly he'll need to calm down a bit, but i'd much rather have a guy who goes over the top than someone who just doesn't seem to care (see: Severin, Scott)
Diamond is an obvious choice who i'd be happy with too, As I would also for Langfield, however i'd prefer if our captain was an outfield player, not a keeper.
So, in short: I just don't know!