LAS VEGAS – As Conor McGregor left his dressing room at TD Garden in Boston on Aug. 17, 2013, to make his way to the cage for his second fight in the UFC, the house lights went dark.

The crowd erupted, and UFC color analyst Joe Rogan marveled at what he was seeing.

“Wow,” Rogan said upon hearing the crowd’s guttural roar for McGregor. “I really can’t remember the last time a guy with one UFC fight – well, Brock Lesnar, but first of all, he’s a 300-pound giant of a man who looks like a freak. You look at him and you go, ‘What is that? Is that even human?’ But this guy’s a normal dude from Ireland with one UFC fight and this place is on its feet.

“I know this is Boston. I know they’re Irish. I grew up here. They go crazy for anything Irish. But this is something unusual. This kid has got something.”

If Rogan only knew how prophetic those words would prove to be.

When McGregor makes the walk to the Octagon at T-Mobile Arena on Saturday to challenge Khabib Nurmagomedov for the lightweight title in the main event of UFC 229, he’ll do so as one of the highest-grossing fighters who ever lived. The UFC doesn’t release its pay-per-view numbers publicly, but McGregor appears to have sold more than anyone who has fought on pay-per-view other than boxers Floyd Mayweather, Oscar De La Hoya, Mike Tyson, Evander Holyfield, Manny Pacquiao and Canelo Alvarez.

It’s a staggering number for a guy who didn’t join the UFC until 2013.

He was on government assistance at the time, but on Saturday, he’ll make a purse that could creep toward $50 million. He’ll earn millions more in endorsements.

He had a vision of how it would play out, even when no one knew his name. In 2013, he said several times, “I’m not here to take part. I’m here to take over.”

Now, he’s a global star, and by any measure he’s turned his vision into a reality. In the cage, he’s one of the best pound-for-pound fighters in the world, ranked No. 2 in the current UFC ratings behind only heavyweight and light heavyweight champion Daniel Cormier.

McGregor, who is 21-3 overall in MMA, is one of only two men, along with Cormier, to hold two weight class championships simultaneously and one of only five to hold titles in two divisions at any point. In addition to Cormier and McGregor, Randy Couture (heavyweight and light heavyweight), B.J. Penn (welterweight and lightweight) and Georges St-Pierre (welterweight and middleweight) are the others to do so.

He’s already among the top individual pay-per-view sellers of all time, and he’s poised to become just the second man, joining Mayweather, to have participated in more than one fight that sold two million on pay-per-view.

The only bouts that have done that are Mayweather-Pacquiao in 2015, at 4.6 million; Mayweather-McGregor in 2017 at 4.4 million; Mayweather-De La Hoya in 2007 at 2.48 million and Mayweather-Canelo Alvarez at 2.2 million in 2013.

It seems a lock that Nurmagomedov-McGregor will break the UFC pay-per-view mark of 1.65 million set in 2016 by McGregor and Nate Diaz at UFC 202. It’s a good bet to surpass two million and is trending, UFC president Dana White said, to reach three million.

McGregor hasn’t fought an MMA fight since Nov. 12, 2016, when he defeated Eddie Alvarez to win the lightweight belt in a fight that set the UFC record for largest gate in history at $17.7 million. The gate on Saturday at T-Mobile is expected to be just over $17 million.

McGregor, who had a child, is expecting another and boxed 10 rounds with Mayweather since his last UFC appearance, has picked up where he left off.

Asked for a prediction, McGregor didn’t miss a beat.

“Domination, his head bouncing off the canvas,” McGregor said. “… He’s a glass jaw. The Chechens, my Chechen friends, the soldiers, they told me they have chicken jaws in Dagestan. And I believe them, because I know a glass jaw when I see one.

“I’ve seen this man wobbled many times. I’ve seen his brother sparked unconscious in another promotion. I know he’s afraid of a smack, and if you’re afraid of a smack off me, that smack will feel like a double-barrel shotgun. I believe [it will end] inside the first. But I have been wrong before, and I have prepared for five rounds.”

He’s a slight underdog, though he scoffs at the odds. And his teammates say he has reason to be confident.

His close friend, Dillon Danis, is one of the elite grapplers in the world and is 1-0 in Bellator. Danis has helped McGregor prepare for Nurmagomedov’s grappling.

“I have the same kind of game as Khabib, but I have more submissions in my arsenal,” Danis said on “Embedded,” the UFC’s internet series. “I have the relentlessness and the wrestling, but I attack a lot more and I’m a little bit bigger. I feel I’m springing a better version of Khabib on Conor every single day.”

McGregor’s probably hit a point of diminishing returns in terms of performance. A win over Nurmagomedov would be massive for his legacy, but it’s his innate sense of marketing and the growth in the marketplace that will make him bigger.

Mayweather is unquestioned as the top draw in boxing history, but he didn’t sell much in his first decade. It wasn’t until he dropped the “Pretty Boy Floyd” persona and turned into “Money Mayweather” that he began to sell in huge numbers.

McGregor has been a draw from the beginning and he’s only been in the UFC for five years. With the rapid expansion of streaming services and over-the-top (OTT) platforms, White believes McGregor’s possibilities are limitless.

“I said on Day 1 when we bought this company that there would be a day when the whole world could watch a fight at the same time,” White said. “We had to make deals back then with all these different distributors all over the world and there was no OTT. Now, OTT is a reality and it works. Look at Netflix and that’s what you’ll see for us.

“So to answer your question, how big can he get? Well, the answer is easy: There is no limit. There are eight billion [expletive] people on Earth. Think of that. Eight. [Expletive]. Billion. Selling five or six million on pay-per-view is nothing when you have an audience like that. It’s a speck of dust.

“And a guy like Conor, who is already a massive star and just keeps getting bigger and more known, what he can do is really limitless.”

McGregor is all about the business, and he does business because he knows when to give a crowd what it wants.

There was a ravenous, bloodthirsty crowd of mostly Irish gathered at the prefight workout Wednesday at the Park MGM. McGregor wasn’t about to talk about whiskey, or his clothing line, or even the grappling game with this group.

He knew exactly the right words to say.

“I’m coming out of that gate fast,” McGregor said. “I don’t give a [expletive] anything: Wrestling, technique, anything. I’m coming for that man’s head from the first [expletive] bell. Trust me on that one.”

He may not win, but he’s going to explode out of the gates and go for the kill early. After five years, there is no longer any sense in doubting him.

More UFC 229 coverage from Yahoo Sports:

• McGregor’s trash-talk game is on point
• Kevin Iole: Who will win McGregor-Nurmagomedov fight?
• UFC 229 could set a major record on Saturday
• Dan Wetzel: This time McGregor isn’t faking the hate