McGregor hopes to challenge 145-pound champion Jose Aldo, second only to light-heavyweight title-holder Jon (Bones) Jones in the UFC's pound-for-pound rankings. And he hopes to dethrone the Brazilian before a record crowd outdoors in Dublin at either Croke Park (his preference given its rich history) or Aviva Stadium.
UFC president Dana White believes McGregor could sell out 90,000 tickets in Ireland. The UFC record is 55,724, set at UFC 129 in April 2011 at Toronto's Rogers Centre.
"It will be the biggest fight that division has ever had. And it will be the biggest payday Aldo's ever had," White said recently.
But first, McGregor (16-2) must dispose of German veteran Dennis Siver (22-9 with one no contest) in the main event of a televised card at Boston's TD Garden on Saturday night.
"Ali needed Frazier, Bird needed Magic and the list goes on and on. And that's what McGregor is for Aldo," UFC boss Dana White said in a recent chat with reporters in Las Vegas.
"But everybody just assumes he's going to walk through Siver. Nobody thought he was going to beat (Dustin) Poirier but now he's just going to walk right through Siver. I don't ever count the chickens 'til they hatch man, believe me, because anything can happen in this sport so we'll see what happens."
McGregor, whose four UFC wins have included three first-round stoppages, is ranked fifth among 145-pound contenders. Siver, who at 36 is 10 years older, is No. 10 on the featherweight pecking order.
McGregor, who fights very well and talks even better, says it's no longer personal as the fight nears.
"As the fight gets closer, I have no thoughts," he said in an interview. "The face becomes blank. Simply a new body type that I must figure out a way to (beat)."
That won't take long Saturday, he believes. McGregor, who has won 12 straight, predicts a victory within two minutes.
With Siver not speaking English and generally averse to trash talk, the pre-fight banter has been less than most McGregor fights.
"I don't engage with cheats," McGregor said in a shot at the German, who was suspended for nine months after failing a UFC 168 drug test in December 2013.
Siver blamed a supplement for the failed test. McGregor isn't buying it, saying Siver tried to hide the doping.
"So I'm sure he's probably on something right now," he said. "I will go in there and I will be ruthless with him. I will really hurt him bad if the referee doesn't step in there."
Siver said he made one mistake in the past, but was clean otherwise. And he insists he is clean in the present and will continue to be so.
It's a measure of McGregor's draw that this is his second UFC main event — the first was a July win over Brazilian Diego Brandao in his native Dublin.
The fight before that, McGregor wasn't even on the main card for his Boston bout with Max Holloway, although he was one of the stars of the show.
"Nothing happens overnight. Sometimes you'll find people that are so different than the norm, like a Conor McGregor," White said in a recent chat with reporters in Las Vegas. "This kid's had a couple of fights in the UFC, (and he's now) selling out the Boston Garden. What he did in Ireland. Even here in Vegas (against Poirier at UFC 178) was crazy.
"Those guys are one in a million."
Reebok has jumped on the McGregor bandwagon, giving the featherweight a featured role in its UFC sponsorship deal along with the likes of Jones and fellow champions Ronda Rousey and Anthony Pettis, and former title-holder Johny Hendricks.
McGregor reacted to the news with typical bluster.
"Congratulations to @Reebok on netting the biggest signature in the game. #StayReady," he tweeted.
But science has backed up McGregor's hype.
Recent tests at the Center for Sport Performance at Cal State Fullerton demonstrated McGregor's athleticism. The Irish fighter broke the lab record for balance, erasing the mark set by pro surfer Keanu Asing, and angular velocity, set by golfer Rory McIlroy.
"All we test in our lab is elite-level athletes. So what we found out today is not that Conor is elite. He's elite compared to the elites," said Dr. Andy Galpin, a Cal State professor of kinesiology.
"Science, baby," said a contented McGregor.
McGregor is fast and furious. He connects with 4.6 significant strikes per minute, a rate 60 per cent faster than the UFC average of 2.83, with three knockdowns in his four UFC fights. And he's never been put on his back in the Octagon.
Aldo made his thoughts clear about McGregor last October after defeating No. 1 contender Chad Mendes for a second time at UFC 179 in Rio de Janeiro with McGregor watching.
"I think the court is complete," Aldo said in the cage after, through an interpreter. "I'm the king, Chad's the prince, and now we have a joker."
Aldo (25-1) has won seven straight in the UFC, bringing his 145-pound title over from the WEC where he won eight in a row.
He won his title in November 2009.
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