Chamberlain, you see, isn’t the only other non-boxer endowed with such incredible physical ability that a lot of people believed he could return to action deep into middle age. Jim Brown, who won eight NFL rushing titles in his nine seasons with the Cleveland Browns, had been retired for 17 years when he appeared on the cover of the Dec. 12, 1983, issue of Sports Illustrated, wearing a Los Angeles Raiders uniform. The headline read “Jim Brown: Are you serious? A comeback at 47? Hey! You’re just what the boring NFL needs!”

Arum, interestingly, had introduced Brown to Ali after Brown’s final NFL season, in 1965. Arum began promoting boxing matches in 1966, at which point Brown asked the new president of Top Rank if he could arrange a title bout between himself and Ali.

Ali met with Brown at Hyde Park in London, where the champ asked the 6-2, 230-pound football legend to try to hit him, as hard as he could. A perplexed Brown then fired a succession of roundhouse shots for about 30 seconds, all of which Ali easy evaded, while occasionally landing stinging, open-palm slaps.

“Ali kept slapping him in the face, not hard, but hard enough and often enough to make the point that as great an athlete as Jim was, he’d have no change in the ring against Ali,” Arum is quoted as saying in Hauser’s book.

Bottom line: Boxing is not like any other sport. Just as there are great boxers who would be utter failures at football, basketball and baseball, so, too are there great athletes in those sports who would fare better trying to pole-vault across the Grand Canyon than stepping inside the ropes against an elite fighter.