breh Terry is definetely not better or much better than Cahill if thats what you are insinuating, the amount of extra work that Cahill has to do to cover for terry lack of pace is incredible, in an ideal world Cahill would be the 3 CB for Chelsea to come in and rotate with 2 other good ones (like godin/miranda for example)Cahill is arguably the weakest player in the first 11 at the moment. It's not really a problem in the league but he ends up looking out of his depth against top strikers/teams in the Champions League.
I've got faith in Zouma and Christensen (great prospect) though.