Although I have a lot of respect for Dmitry, I think he would lose this fight. It would be very difficult to find a boxer under 180lbs who would beat Rocky Marciano; maybe impossible.
Can't see Bivol hearing the final bell when Rocky would not be deterred by his quick little flurries and graceful footwork. Rocky would invest in body shots, hitting the arms, hip, chest, whatever he could land on until Bivol felt like he had been hit by multiple speeding motor scooters. Eventually, Rocky starts to land some heavy leather to the head and Bivol goes down sometime in the 8th. Rocky swarms all over him and finishes him in the 9th. Bivol would be up 5 rounds to 3 at the time of the stoppage.
Flipping Bivol. Never mind Marciano I want to see him deal with the best 175 puncher of his own generation before he enters the Time Machine to fight an unbeaten 185 ATG incredible punching machine with unlimited stamina. Once the…admittedly…very skilled Bivol dispatches Beterbiev then I’ll entertain the idea of him even getting into the ring with the Great Man. Oh ok then you’ve persuaded me. Marciano stops him late while behind on points. Isn’t that the standard response when Rocky comes up against skilled fighters past and present with a very good defence? In this case I actually think this is how it would play out. But over 12, not 15 rounds, Rocky better not hang about or he might…just might…find himself too late in delivering the final KO blow.
I’m used to imagining Rocky struggling against much larger foes, and wondering if he could find a way, in this case there is not nearly as much gap between the contestants size wise. I think Rocky would hammer down Bivols guard by wearing out his arms and body. At that point it’s game over but he would be a mess facially, and probably behind on the cards. If he can close the show inside 12 he will win. Over 15 almost certainly, but over 12 Bivol might grab it on points if he can take the punches, which is sort of unknown. Very hard to pick anyone between about 175-190 lbs. over Marciano.