Answer: NOTHING.

Marciano was NOT a virtual 1-armed fighter as Frazier was. Rocky had dyn-O-mite in each fist. Frazier threw no more than 10 right hands the whole night on March 8, 1971 and STILL pounded Ali to a pulp by the end of the fight. Rocky Marciano would have bludgeoned ali with BOTH fists.

Marciano hit a little harder too. So if Frazier was able to beat ali, knock him down, then:

Rocky Marciano KO over Muhammad ali, Round 9.