Even when Diaz was still in the UFC and GSP was just a title contender, Diaz couldn't beat the upper echelon fighters in that division. He lost to Parisian (before he was a chubby burn-out and was a serious contender) and Dego Sanchez (I know that's spelled wrong, don't care). Diaz is tough, and I've never seen him really get beat up, but if he comes back into the UFC he'll be what he was before, a stepping stone for real contenders en route to a title shot. But, this is the organization that gives fighters title shots after one lack luster fight with a controversial decision in the octagon.