We're better off spending good chunk of cash with a young, quality defender like Ogbonna, then resigning Sorensen back for peanuts.
Imagine one of our defenders gets injured. We're fucked. Our strength from our teams starts from the back, our wall. Caceres is decent/good as a CB. But nothing more. You can tell our backline is a bit more shaky with him there. Anyways, Caceres can really only fill Barzagli's spot. Whereas Ogbonna could fill in any of the 3. Ogbonna is healthy competition for our three CBs as well, Caceres could never take those spots away from them. As for Sorensen, the kid doesn't have what it takes to play at Juventus. Just like Immobile and others, he had more hype than promise. He doesn't have what it takes, especially in the CL.
Depth players:
CB: Ogbonna/Caceres
RWB: Caceres/Padoin
LWB: Peluso/Giaccherini
CM: Giaccherini/Pogba
ST: Giovinco/Vucinic/Matri/Quag
A great bunch of players coming off the bench.
Also, at this point in time Jovetic would be a luxury. We already have Tevez with Giovinco or Vucinic coming off the bench for him in the case of any injury/exhaustion.