I suppose in theory
Wladimir Klitschko could jab and grab and smother his way to a decision.
But I'd expect Rocky to get him out of there sometime with his sheer brute power and aggression. And Marciano was clever, he looked for weaknesses and had a knack of not becoming predictable in his pattern and pace of fighting.
The guys Klitschko has been beating have been mostly awful, and he's been KO'd twice in his prime, and troubled by lesser fighters than Marciano. Some of these "challengers" he fights are just there for a payday and dont even care to win, at least Don ****ell came to fight !
Wlad's not a great fighter and I think he'd be flakey against a true all-time great puncher/fighter, for example Rocky Marciano.