The problem Marciano would've had against Ali would be 'Cuts', Ali would cut fighters up. I think the Frazier/Marciano comparison gives leeway to thinking Rocky might've got some shots in, but his strength was the right hand and the only two times Ali was seriously hurt was when he got caught flush by "Enry's 'Ammer" and when Smokin' Joe caught him in the first fight in round 15. Both LEFT hooks!