Filed under: UFCCan Nick Diaz make a triumphant return to the UFC and beat B.J. Penn? Can Matt Mitrione stay undefeated and beat Cheick Kongo? Will Mirko Cro Cop show he still has something left against Roy Nelson? Is there any reason to buy this pay-per-view now that Georges St. Pierre is off the card? We’ll answer those questions and more as we predict the winners of Saturday night’s UFC 137. What: UFC 137: Penn vs. Diaz Where: Mandalay Bay Events Center, Las Vegas When: Saturday, the prelimin…