This is a nearly complete version of the classic 1st Robinson-Basilio fight (I believe it's just missing part of the 1st round). In this fight, Basilio demonstrates both his ATG toughness and technical skill as he continually walks down the older, but bigger and still very talented champion and shakes off the kinds of bombs that previously flattened Bobo Olson and Gene Fullmer. Much like Frazier's victory over Ali, this fight would prove to be the zenith of Basilio's HoF career, and he was never quite able to reach the same heights again.
How far past his best would you say Robinson was in this fight? To me he looked like he still had a lot left.
He made his pro debut 17 years and over 150 fights prior to this. Of course, past prime Robinson was still good enough to give the best of the rest all they could handle, if not more. Basilio was similarly disadvantaged, though, being outweighed by 7-10 pounds and fighting at a weight class he hadn’t come close to growing into. I’d say they fought on even terms. Basilio was the better man this night and Ray reversed the tide in the rematch. Great fights between great fighters, even if they weren’t at their very best. Basilio still gets underrated, especially his skills, which were exceptional. Quintessential infighter.
SP pretty much hits the nail on the head - Robinson was visibly a step or two slower than in his prime (but still fast in a general sense) and his stamina wasn't as reliable as it once was, but this was offset to a degree by the fact that Robi now had a size advantage over Basilio (which he wouldn't have had in his prime) and was hitting harder than at any previous stage of his career.