Andrew Bogut or Yi Jianlian
Yi is currently available and I haven't been too fond of how Bogut has been playing lately. I've already got 4 other eligible centers in Bargnani, Camby, Horford, and Okafor who have all been reliable rebounders thus far with the exception of Bargnani. So ignoring rebounds, Yi seems to have the edge over Bogut at the moment, but I'm not sure if I should give up on Bogut just yet. At the same time though, I don't know how much longer Yi will be available.