Swansea, with an inferior squad and "attacking" playing style managed the same amount of clean sheets as us last season and Caulker played pretty much every game he was available for them. I'd give him the step up.
And play him ahead of who? Vertonghen (assuming he signs)? Or Kaboul? Or Gallas? Or King (when fit)? Maybe Daws...
We need every point we can get to finish top 4
Playing in a team like swansea which has so much possession can only help defenders as they're under the cosh less. Compare playing for a team which has 60% possession against playing for one which has 50%. that means the opposition only have 40% compared to 50% so you thereore have 20% less defending to do (1 - 40/50). that can only help you look good (am not saying that he isnt though)