Outrageous that some posters here think Frazier would put Lyle down in under five or six rounds. If peak Joe doesn't get caught nasty he will absolutely drown Lyle later on, especially with the stamina and output gap, but Ron was one of the toughest sons of a gun to ever lace them. Back to back trenches against Shavers and Foreman, past-it put a traumatizing beating on the ever tough Bugner. He only seemed helpless against boxing cuties, where perhaps he was thinking too much. More on-topic: peak Joe was startling. Amazing rhythm, laser-focused and locked on his target.
Without a doubt--Frazier was never the same after the FOTC. However, I still think post FOTC Frazier up to Manila could handle Lyle. But after that Joe really had nothing left--Lyle beats him.
Quarry was effective against a green Lyle in the Irish American home turf of MSG in the 70s. We know Frazier was better the Quarry. But styles play in. Quarry boxer puncher were Frazier was walk in slugger 98% of the time. If Joe walks straight at Lyle and we go with the Lyle that KOd Shavers or almost Foreman Joe could be in trouble. Ron was stronger and more powerful then Bonavena and Quarry who temporarily backed up Joe. Lyle if he could be aggressive as he was against Forman has the power to stop Frazier like Foreman did.