For much of the past decade, Floyd Mayweather, Jr., has been the best boxer in the world. This, anyway, has been the judgment of many experts, including the expert known as Floyd Mayweather, Jr., whose sport provides him with plenty of opportunities to demonstrate his supremacy but no clear way to prove it. He won his first championship belt in 1998, when he was twenty-one, and he has accumulated many more since. But so what? Boxing has countless champions, yet no central authority, and therefore no neutral party to rank the trophies that fighters are awarded by miscellaneous organizations, associations, and federations. Matches are negotiated and scheduled by the boxers and their representatives, which means that the sport has nothing resembling a season or a post-season. Boxing, rather like life, is just one damn fight after another.

Mayweather typically fights at welterweight, which has a limit of a hundred and forty-seven pounds, near the middle of the sport’s seventeen weight classes. The unofficial ranking of the best fighters in all the classes is known as the pound-for-pound list: the idea is to compare boxers’ abilities and achievements as if the boxers were the same size, and the result is an ongoing argument among fans and journalists and the fighters themselves. In 2007, when Mayweather announced that he was taking a “vacation” from boxing, virtually everyone agreed that he was at the top of this list. In 2009, when he went back to work, he submitted to an interview with Brian Kenny, on ESPN’s “SportsCenter.” Kenny introduced him as “the former No. 1 pound-for-pound fighter in the world,” and Mayweather immediately objected.

“I’m not no former No. 1 pound-for-pound fighter,” he said. “I’m the best fighter in the sport of boxing. No one has dethroned me.” Mayweather’s physical gifts are almost uncannily well suited to the demands of his job: he is strong but skittish, good at punching, and even better at not getting punched. His high opinion of himself is both accurate and, in a chaotic sport, useful. If no one is empowered to crown him, he is happy to crown himself.

On that day in 2009, Mayweather was promoting his comeback fight, against a skilled Mexican veteran named Juan Manuel Márquez. It was a respectable match, but one that Mayweather was expected to win easily—as, some months later, he did. Kenny, like many observers, wanted to know when Mayweather would face the one man who challenged his claim to pound-for-pound supremacy: a frenetic Filipino named Manny Pacquiao, who had just flattened three highly regarded opponents in a row. Mayweather did his best to project lordly indifference. “If Pacquiao’s in front of me, and it’s time to fight Pacquiao, then I’ll take care of that,” he said. But, as Kenny pressed him, Mayweather’s manner became, like his fighting style, somewhat defensive. “I’ve never ducked or dodged no opponent,” he said. Pacquiao, he implied, wasn’t yet worthy of him. “All of a sudden, he got a couple wins—now you say, ‘Throw him in there with Floyd Mayweather.’ ”

In the years that followed, Mayweather and Pacquiao kept fighting, without finding a way to fight each other. Sometimes the two sides negotiated; at other times they refused to; at one point they had a vehement public disagreement about whether they were in fact negotiating. As anticipation for the unmade match grew, so did frustration. The sport’s inability to give fans what they obviously wanted came to seem like a kind of market failure. Boxing promoters, a species not known for munificence, seemed to have squandered an opportunity for a historic payday. Half a century ago, boxing was one of the country’s most popular entertainments. In the nineteen-sixties and seventies, Muhammad Ali helped to create some of the era’s most memorable cultural moments. Now, it seemed, boxing couldn’t even find a way to get its two top names into the same ring.

Then, this January, Winter Storm Juno spiralled up the East Coast, causing Governor Andrew Cuomo to close New York’s subway system and, nearly as significant, inspiring Pacquiao to delay a scheduled trip to the city and stay where he was, which was Miami. He decided to take in a Heat game, and when he got to the arena he found himself seated across the court from Mayweather, who was in town on his way to Jamaica. At halftime, they met, for the first time, and after the game they repaired to Pacquiao’s hotel room. The meeting helped persuade their various representatives to negotiate in earnest, and on February 20th Mayweather posted online a picture of a signed contract, along with an announcement:

What the world has been waiting for has arrived. Mayweather vs. Pacquiao on May 2, 2015, is a done deal.

The announcement marked the end of a six-year wait, and the beginning of a furious ten-week period during which the two boxers juggled the athletic requirements of training camp with the promotional requirements of selling what was becoming known, grandly though not incorrectly, as the Fight of the Century. The century, after all, was still young, and certainly no boxing match in the previous fifteen years had generated as much interest as this one already had. The announcement of the fight coincided with a slight change in Mayweather’s estimation of Pacquiao. “You’ve got two future Hall of Famers in a mega fight,” he explained, one afternoon in Las Vegas—pleased, now, to view Pacquiao as a fellow-great, if not as an equal. “He’s a very, very reckless fighter,” Mayweather added, with a trace of pity, and maybe also of envy. “I could have had the same type of career, but my career probably wouldn’t have lasted this long, and I probably wouldn’t be at this point, if I was a reckless fighter like that.”

Reckless fighters pay a price, but so, too, do cautious ones. Unlike Pacquiao, whose record included five losses and two draws, Mayweather was undefeated, forty-seven and oh. But, whereas Pacquiao had a legion of fans who stuck with him through frequent wins and occasional losses, Mayweather, an extravagant spender but a careful boxer, didn’t inspire much loyalty. He has lived in Las Vegas for nearly twenty years, but he is still booed when he fights there. When I asked him whether boxing was still fun, he spoke like an entrepreneur whose success has outlasted his passion. “I don’t really enjoy it like I once did,” he said. “It’s my job: I go to the gym, I train, I go home, I do what I have to do. At one particular time, it was fun. But I’m to a point to where I’m really over all of this.”

Mayweather was speaking in a small tent that had been erected in the parking lot of his gym, Mayweather Boxing Club, which occupies a tinted-glass storefront in a strip mall in Las Vegas’s Chinatown, about a mile and a half west of the Strip. This was his official Media Workout day, designed to serve empty calories to hundreds of news-hungry journalists who had flown in from around the world. There were venders selling Mayweather T-shirts and hats, and the media scrum was augmented by a similar-sized contingent of friends and fans. In this small world, Mayweather could play the role of crowd favorite. When the wind picked up, rattling the support rings against the tent poles, his publicist, Kelly Swanson, intervened. “They tell me a bad storm is coming,” she said.