Julio Ceasar Chavez would have been a stern test, in my opinion. Castillo gave Floyd fits the first time they fought, and he was a poor mans Chavez (actually Chavez's sparring partner which got him to the elite level. I go back and forth on how this fight unfolds, but that Chavez was relentless and threw some gorgeous combinations. Floyd was an ATG 130 pounder also, so I can see a solid case for him winning that one as well.