You asked me the question which I tried to escape lots of times after Fiorentina extended Dainelli's contract, but it seems that there is no way. :wink:
First of all, let's suppose that Gabriel Milito will be our regular left centre back for the next season, thus we have to think of the best available defender to partner him. At first, I thought about a rotation system among Grygera, Criscito, Zebina and Boumsong for the right centre back position, in this case the right back position will be affected too, a thing which will add more instability to the defence line. Of course, Chiellini can't partner Milito, as both of them are left-footed. Hence, signing another good centre back will be essential.
The centre backs whom we're strongly linked to now are Barzagli, Heinze, Cris, Cannavaro, etc..(I don't remember more defenders right now). Cannavaro has said that he wants to win the Champions League, hence I don't think he'll leave Real Madrid. With the presence of Chiellini and Milito, I think we're in no need of Heinze as a left centre back and he doesn't normally play as a right centre defender, besides I read that Real Madrid are in pole position to sign him. Therefore, I see that the only realistic targets now are Barzagli and Cris. The latter is solid experienced defender who won't cost us more than £8m, still he is a bit old and he hasn't played in Italy before. Whereas the former is younger and has a good experience in Italy, yet I do think that he isn't that tough and a bit inconsistent, also his performance hasn't convinced me after the World Cup whatsoever.
To sum it up, I'm between Barzagli and Cris, but if they're the only options in hands, I may go for Barzagli.