It happened on March 31, 1988. Muhammad Ali, from the garden of his house, yelled at some onlookers: “This has not found out that I am the best boxer of all time.” This was Davis Miller, former kickboxing champion turned video store clerk, ten years younger than him (35 by 46, an eternity in the ring) and healthy, definitely healthy; Ali, on the other hand, had been living with Parkinson’s for several years. Miller went into his house because he saw the RV parked inside it, and he knew that Ali moved across the country in RVs and buses to travel leisurely. Miller is the world’s leading expert on Ali, he has been studying him obsessively for more than half a century, ever since, in his words, his figure saved his life and brought it back to sports when he was a child. That day, after talking to him and getting him to sign some magazines, Ali played a joke on him and then they went on their guard.

It is a brilliant scene that Miller, who thanks to his reports, profiles and interviews with Ali became a sought-after writer, writes with talent in In search of Muhammad Ali, story of a friendship (Errata Nature, 2016). Ali, whose Parkinson’s was becoming more visible, had come clumsily down the steps of the motorhome, nearly falling. And then he raised his guard, wanting to box. Miller played along (the punches weren’t coming within six inches of each other), Ali took off his watch and yelled at the onlookers who were beginning to crowd the outfield fence. The largest had returned ten years after his withdrawal. He got into position and began to dance, letting go of his legs. Anyone who has seen Ali boxing on video, or live if she is old and lucky, will know that this dance is somewhat mesmerizing (“flies like a butterfly and stings like a bee”). “He threw another jab at me, then a second, and a third. He wasn’t half as fast as he had been in 1975, when I trained with him, but his eyes were alert, bright as two pieces of electrified black marble; I saw everything, I was completely relaxed,” writes Miller, who recalls that this is one of the reasons old fighters return to the ring again and again: there are hardly any moments when they feel more alive than when they box.

Guilty parried Ali’s punches: Miller was fighting the champion, but also a man with Parkinson’s. “I’m going to let him get tired, he’ll get tired fast,” Ali said. And Miller pretended that he was getting tired. “He got scared!” the champion yelled. There was one of the last fights won by Ali, and also a luminous certainty that has to do with the nature of an elite athlete, one of the greatest of all time: instinct governs everything, even an old body or sick. I think about the retirement of Messi, the greatest soccer player, in Miami, and about the years he will spend there and the way his rivals will face him or hold him down. If there will come a season in which the striker is so slow that a defender who dedicates himself to football for him, whose life has changed thanks to him, his legs shake, not because the Argentine passes over him like a plane, but because he is going to easily take the ball from him and he feels bad, like one of those boys who hesitates between killing his father or lifting him on his shoulders and carrying him himself to the goal.

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