Brock Lesnar wins this one if they both fight in their prime. Lesnar was subbed by Mir with little to no knowledge of submissions in his second ever MMA fight on the biggest stage. Take that in for a minute... Lesnar was a massive man, a Division 1 NCAA Wrestling Champion. He manhandled the Texas Crazyhorse. Werdum was a decorated BJJ Champion who in the latter part of his career had a few knockouts but in his prime he was an average boxer. Not enough to stop Lesnar, Shane Carwin couldn't and he hit like a Mack truck. Werdum would not be able to stop Lesnar from taking him down, in fact may go to his back thinking he had an advantage but the sheer strength, size , and wrestling of Lesnar would of been too much. Note: I'm referring to the Lesnar pre-diverticulitis. Once he had that he was never the same, was just an average UFC fighter.