Obviously Ali, but I think Bonavena would be entertaining and exciting, possibly FOTY material, he's been in deep water with the best of them, Marciano wins but it would be a great slugfest with technical inside moments
Yes, if Rocky would replicate pro Frazier's career he'd certainly pick up losses early on. Bonavena. Jones, Machen and Chuvalo within about his first two years would be very tough. But due to his lesser amateur pedigree there's little reason to believe he'd be matched like that. More that he would be matched in the pace he was in real life, so he doesn't mix up with ranked contenders until 69-70.
An over the hill Henry Cooper did reasonably well vs a prime Bugner. I believe it was Cooper's last fight. I know you have the difference in styles a boxing math isn't perfect, but a prime Henry Cooper wouldn't beat the Rocky of 1955 who beat Moore and despite his size, can't see Bugner defeating Rocky.
But he's talking about a Rocky in his 9th year as a pro after fights against Ali and Foreman. So that would be Rocky in his final year, with the mileage of fighting those two.
Yeah exactly that's I'm trying to say. Would a prime Marciano be a favourite over Bugner ? Of course. But when you take into account Marciano would have 9 years of wear and tear if we're following Frazier's career path. Taking into account Marciano's actual career was only 8 years I believe. So Marciano would be coming off losses to Ali, Foreman, and I think most people would agree Marciano loses these fights. He then has to fight a Bugner who's alot bigger than him who fought arguably the best fight of his career vs Frazier. There's alot of questions. How does Marciano react to losing as a professional ? How much wear and tear would he have at this time ? It's not out of the realms a past his prime Marciano coming off losses with alot of wear a tear loses to an in form Bugner.
Frazier had an impressive come back after Foreman. Sure Bugner was not a puncher, but he was very tall for the era, moved well and had a good jab. Then Ali and after that Quarry, who was on perhaps his best run. An old Ellis was more of a stay busy fight, but then Ali and Foreman back to back. Imagine a fighter today having six fights like that over three years after suffering one of the brutal beat downs in boxing history. I think Rocky had the same mental toughness, but he would be older at the same amount of years as a pro.