From those that saw him it seems like Sullivan’s peak was in 1882-83, by 1885-86 he had become an alchy and usually came into fights out of shape. However, what I’ve also noticed when reading contemporary reports about Sullivan throughout his career, is that he was gradually getting more skilled throughout his career. Mike Donovan was with Sullivan since 1880, and felt that the version of Sullivan that beat Kilrain was a better boxer than Sullivan from the past. Could this be a Foreman-like situation; Sullivan in his youth being a wrecking machine, but best displayed his technical prowess long past his best.
Physically it was probably the first Paddy Ryan fight. He didn't take long to hit the skids after that. Some observers talk of his punching form improving after that, but I doubt that his peak was later than 1883. Sure as hell could be a Foreman type situation.
I suspect Sullivan's best was mid-1881 -- I think Madden was influencing him to punch straighter -- to about mid-1883, when he started adopting an 'I train if/when I need to' attitude. Interesting to hear from Mike Donavan, a great fan of Sullivan. When Donovan spared a young Sullivan, he said that only because Sullivan was still a swinger was he able to get through the spar. The Sullivan who fought Kilrain was coming back after extreme illness and might have had to somewhat economize his approach. I speculate.
