Yeah, and Big Show was notorious for being terribly out of shape. He was a smoker and ate lots of fast food, and he barely worked out. This was in and around the ECW revival, when he was champ. It wavered from there. Like Pyrus said though, Prime Big Show was really, really agile for his size, and obviously super strong. I think he murders Rhonda Rousey pretty easily. Kimbo Slice too, who has been shown to have major stamina problems of his own, as well as having next to zero ground game.
I feel pretty comfortable giving Show, in his prime, those two wins without much thought.