UFC Featherweight Champion Conor McGregor stills draws throngs of reporters despite his loss to Nate Diaz earlier this year. Saturday’s fight might determine whether he remains a fight fan’s draw or becomes something bigger. (Isaac Brekken/Getty Images)

No championship will be on the line, and the winner will not be assured of the next welterweight title shot. Neither fighter is even a welterweight, for that matter, other than for this bout and for their meeting in March. And as rematches go, this one was not born out of necessity or even popular demand, the emphatic finish of the first fight having left nothing unresolved. In the old-school way of looking at combat sports, this bout is meaningless.

But for Conor McGregor, Saturday night’s second clash with Nate Diaz in the main event of UFC 202 in Las Vegas means everything.

McGregor is at a crossroads in mixed martial arts, a sport he has transformed. From his first appearance in the UFC three years ago, the Irishman spoke of pursuing the gold, and he rose through the ranks swiftly on the strength of loquacious self-belief backed by unblinking offensive flair. But as soon as he stunned long-reigning featherweight champ José Aldo with a 13-second knockout in December and wrapped the shiny belt around his waist, it became clear that it was not his ultimate prize.

McGregor looked right past the line of 145-pound contenders and set his steely stare on the champs at lightweight and welterweight. These, he knew, were the money fights. Title defenses could wait.

Nate Diaz attends the UFC 202 news conference on Wednesday. He’s convinced he’ll beat Conor McGregor again. (Erik Verduzco/Associated Press)

“The only weight I care about is the weight of my checks,” the 28-year-old said. “And they’re super heavyweight.”

Indeed, when McGregor grabbed the title from Aldo at UFC 194, the event drew a reported 1.4 million pay-per-view buys. The clash with Diaz at UFC 196 reportedly reached 1.5 million households. (These figures are based on reliable industry estimates; the UFC does not reveal financial or viewership numbers.) That means McGregor has headlined two of the three biggest PPVs in the company’s two-decade history. He gets a piece of that action.

Not coincidentally, money has been the story in MMA of late. Last month the UFC was sold to entertainment behemoth WME-IMG for $4 billion. This week a new organization called the Professional Fighters Association, backed by the players’ unions of all the major professional sports, is in Las Vegas trying to persuade UFC fighters and managers that collectively they can share a bigger slice of the pie.

The timing could not be better for that sales pitch. Fighters are starting to follow the lead of McGregor and going after “moneyweight” paydays of their own. Within the past two months, four UFC championships have changed hands, and all of the new belt holders — Tyron Woodley at welterweight, Amanda Nunes at women’s bantamweight, Eddie Alvarez at lightweight, Michael Bisping at middleweight — have set their sights on bouts more lucrative than what the next challenger in line would bring.

McGregor, naturally, is after the richest of all money fights. He has been engaging pound-for-pound boxing king Floyd “Money” Mayweather in banter aimed at drumming up interest in a fight for which both have attached a $100 million price tag. It’s a laughable concept for a fight — McGregor has no chance in a boxing ring, just as Mayweather would be lost in an octagon — but the money is nothing to snicker at. And in today’s spectacle-loving popular culture, the pugilistic circus could very well come to town.

Not if McGregor loses Saturday, though. The Irishman would maintain his star power within the MMA world, where fans understand that he’s competing outside his weight class and still would have an Aldo rematch on his docket. But any significant crossover appeal in the mainstream culture, sports or otherwise, would be doused. And that’s what McGregor has been after all along.

Conor McGregor trains during an open workout on Aug. 12. (Isaac Brekken/Getty Images)

McGregor (19-3) got himself in this predicament with admirable fearlessness. Though the UFC booked him in favorable matchups early in his career, the Irishman has faced up to every challenge placed in front of him — even when the stakes were high and the notice short. He was booked with Diaz (19-10) only after then-lightweight belt holder Rafael Dos Anjos was injured and had to drop out of what would have been a superfight, champion vs. champion. McGregor accepted Diaz as a late replacement and, because there wasn’t time for the new opponent to have a proper weight cut, allowed the fight to be contested at 170 pounds.

That came back to haunt McGregor. He landed hard punches repeatedly in the first round, but Diaz took everything he could dish out and was still standing. “Usually, when I fight a man in the division I am champion in, they crumble under those shots,” McGregor said. “But Nate took them very well.”

He took them better than McGregor did. The Irishman tired from putting so much into his punches, and in the second round a bloodied but fully energized Diaz found his range and started connecting with momentum-shifting punches. After being wobbled by a left hand, McGregor desperately shot for a takedown. Diaz, a jiujitsu black belt, seized the moment, quickly wrapping up a rear-naked choke and eliciting a submission.

Though that finish was as decisive as they come, each fighter has a reason for optimism in the rematch. Before running out of gas, McGregor insists, the first fight was his. “I was controlling the contest,” he said. “I was slapping the head off of him.” As for Diaz, well, he did what he did on 10 days’ notice. This time he has had a full training camp.

The hype ramped up Wednesday at a Las Vegas news conference. McGregor arrived a half-hour late, at which point Diaz, having said all he wanted to say, got up to leave. As he was walking out with his entourage, there was an exchange of insults and expletives, followed by water bottles and energy drink cans. A visibly perturbed Dana White, the UFC president, called the media event to a premature halt.

Before the chaos, though, Diaz had offered a sober assessment of the fight and its buildup. He had seen promotional footage from the McGregor camp, the walls adorned with enlarged photos of punches landing on Diaz’s face. “Who does that?” Diaz said with a little smile. “Trying to make yourself believe something? He’s trying to hype himself up, but when he goes to sleep at night, he remembers what happened last time.”