Its often tough to say with some guys who were hot and cold. Maybe it boiled down to their training habits or maybe they were just basket cases. Im thinking the likes of Zab Judah, terry norris, Golota etc. They certainly never appeared to be out of shape.. Then as you mention Duran, or someone like Hatton, who became fat fucks after fighting but always came to give it their all. James Toney has to be in here, he lost a few that were just inexcusable for a guy with his skills. Chavez jr is one, though he was never all that good, he was obviously entitled and didnt like to train, his loss to Brian vera was hilarious. Broner as well, he might have lost the same fights no matter what, but if he took training seriously and stayed at his proper weight class he couldve done more.