If you look closely, it is very apparent that Rocky's left of part follicle #234 KO's Walcott. [ame="http://www.youtube.com/watch?v=8DR30YzZpu8"]http://www.youtube.com/watch?v=8DR30YzZpu8[/ame]
I think Rocky will be one of the most discussed heavyweights for all time. For example, look at how he feinted a jab before launching the Suzy Q on Walcott. As Walcott prepared to counter Rocky's 'jab', he was completely unaware of the thunderous right hand on the way. Rocky purposely took Walcott's eyes to the wrong place. That false jab was a distraction. And that's part of what made Rocky a clutch fighter. He knew how to get the punch to the target in emergency situations. This is why although Rocky might likely lose to certain fights, you still can't count him out entirely. He'll surprise you. Finding a way to win was his specialty.
rocky would probly have some problems in 4 rounders with mehaan and sullivan most other heavies i see rocky having a better chance against them then they against him.
I don't rate Rocky head to head against most of the top 10 all time great heavyweights. The reason you listed, however, is the reason I don't see to many outside the top 10 getting the upset W. (Klitschko's are the only ones I can think of.) Great skill and toughness was what you needed to beat Rocky, and from a tangible standpoint, really all you needed. But if you factor in that intangible ability to make it to the finish line, mission accomplished, that only the greatest in history truly possess, well, without that mythic quality, you'd find it very tough to beat the Rock.
If Marciano had fought on, then his next opponent would probably have been Willie Pastrano or Tommy Huricane Jackson. Not much risk to the 0 there. Patterson is the outstanding challenger only in hindsight, and it is likley that Marciano would have had at least one or two more fights before facing him. In the final analysis, age would have probably have been the first opponent to take Rocky Marciano's 0, whoever it used as its agent. The one truly unbeatable opponent in boxing.