If sanders came in against vitali 20 pounds lighter, I think it would have been much more competetive than it was. I don't know if Sanders could have pulled it off but it would have been interesting
I would say Sanders was in similar shape (or rather out of shape) against both brothers, despite some weight difference. He gave both Klitschko's a lot of trouble in the first round (I think that technically Vitali should get the count), the difference is that Vitali had good chin and when fight continued Sanders did not look that great anymore. IMHO the difference between those fights was connected rather with the difference between brothers chins than with the shape of Sanders. Both Klitschko's followed their usual strategy, which did not work at all against tall southpaw with fast hands and good power (fortunately for them, there are not that many in HW). Vitali had just better chin, so he was able to continue and fight back... and since Sanders stamina was shot at this point, it turned out to be enough.
Sanders only real asset was a deceptively quick and powerful left hand from his natural lefty stance. A lot of what happened with Wlad was due to overconfidence and surprise. Vitali is I believe a bit more durable, and had the advantage of knowing exactly what to watch for. The result doesn't change no matter how good shape Sanders comes in.
It wouldn't have matter. Once Sanders realized Vitali chin was completely different than Wladmir's it was only matter of time.
same result. Sanders didn't lose because of fatigue. He lost because Vitali, after the second round moved to his left or back after throwing punches. When fighting a southpaw counterpuncher with fast hands you have to move left after throwing a right or else you're in range of getting cracked. Wladimir found this out and so did Vitali. The only difference is Vitali adjusted.