Of course, this entire discussion is hypothetical, including the premise which you provided. The amount of luck, timing, opportunity involved in every success ever is obviously a huge part.
Well, of course, because it was allowed back then, but those players who endured them weren't from another planet, and when we are talking about one of the fittest players in the history of the game, regardless of the rules, then the logical conclusion would be that he would be able to endure them the same way.
Of course, but if there was one thing in which he was absolutely ahead of his time and generation, it was his physical fitness, and the combination of physical attributes such as pace, acceleration, leap, upper body strength, stamina, endurance, etc. Defenders of that generation had never seen anything like that.
Edit: Your username is rather apt for this discussion.