Considering that Conor McGregor vs. Nate Diaz is now the signature rivalry of both men’s careers, it is remarkable that it happened almost entirely by accident. At the time of their first meeting, at UFC 196 in March of 2016, McGregor was already the sport’s biggest star, the UFC featherweight champion and about to try and add the lightweight belt to his collection. In contrast, Diaz was a popular veteran with little visibility outside the MMA bubble and a fringe contender who was largely seen as having hit his ceiling competitively as well as in terms of celebrity. The two were on very different trajectories and probably would never have fought one another if not for Diaz’s willingness to step up on short notice when lightweight champ Rafael dos Anjos was forced to withdraw from the main event.

UFC 196, of course, changed everything for both fighters, as well as for the Ultimate Fighting Championship. The first crucial element was that Diaz, a veteran trash talker in his own right, managed to match the voluble Irishman one-liner for one-liner in the lead-up to UFC 196. Diaz coined the memorable “touch-butt with that dork in the park” in reference to Ido Portal, one of McGregor’s trainers, but more significantly, the two collaborated to hype the fight through the roof on just two weeks’ notice. Even more importantly than their work on the mic, the in-cage product delivered, as 4-to-1 underdog Diaz weathered a first-round beating to choke out the flagging McGregor in the second round of a sensational fight.

With that, a rematch was almost a foregone conclusion, and it promised to be massive. McGregor’s star seemed undiminished for the moment, while Diaz—a born iconoclast whose combative history with his UFC bosses was part of his anti-hero charm—suddenly had a kind of clout he had never before wielded. The rematch was scheduled to headline the planned blockbuster UFC 200 card in July, but when McGregor balked at some of the publicity obligations, sending out a retirement tweet in protest, the promotion called his bluff. Even after the featherweight champ backtracked the retirement talk and expressed his willingness to meet the UFC halfway, McGregor-Diaz 2 was bumped to UFC 202 a month later.

When the rematch finally came, it delivered as well. In the biggest MMA pay-per-view event to date, McGregor avenged himself via majority decision in a fight that, while not quite as sensational as their first meeting, was action-packed and very close. Afterward, McGregor remained the sport’s preeminent star while Diaz, in a rare example of stardom rubbing off, has maintained a degree of next-level celebrity in and out of the sport. In the four years since UFC 202, any time potential matchups for the mercurial McGregor are discussed, the notion of a Diaz rubber match inevitably comes up, as if it is an ace in the pocket of both men and the promotion. And in the final analysis, the McGregor-Diaz clash is not the only one that remains unresolved: While the UFC axing McGregor from UFC 200 was a slightly surprising power play, the fact that UFC 202 outsold it by a significant margin—despite the promotion loading UFC 200 with practically every other star on the roster—is an eloquent counterargument.