Has Valuev ever been knocked down, professionally? Wlad's a good fighter, but he has serious flaws. First of all, he gets tired rather quickly at times, punching himself out. See his loss against Ross Purrity.
YouTube - Wladimir Klitschko Vs Ross Puritty Part5
Puritty has 20 losses out of 53 fights, too. He lost to Brewster and Sanders, with Sanders being a definitive loss since he was really just completely destroyed by him. To Brewster I think it was also punching himself out, although I admit that fight looked very wrong. It seriously looked like he was drugged or something. His chin will be a major problem, since Valuev packs a heavy left jab that has knocked people down (barrett). I think Wlad will start out strong, go for the head and halfway into the fight he will be spent, totally tired. That's when Valuev will score a jab to the chin and Wlad will go down a few times.
My question is, has Wlad ever fought against someone taller than 6'6? Punching above your head wears you out MUCH faster than punching level with your head or punching down (and many of his opponents were shorter). And Valuev is quite a bit taller than Wlad. That's why I think stamina will be a problem for Wlad.