The best boxer in a bearing adjoin one of the better names in the Ultimate Angry Championship.
Floyd Mayweather Jr, admired - afore his retirement - as the world's best pound-for-pound boxer, will activity UFC ablaze Conor McGregor in a light-middleweight battle challenge in Las Vegas on 26 August.
But how and why did the activity appear about? Does McGregor accept a chance? What appulse will it accept on the sports? And is it all aloof a exploited circus?
BBC Activity takes a attending at the history and the acknowledgment to the contest.
Why is it happening? Quite simply... money, with both fighters accepted to acquire up to $100m (£78.5m).
After Mayweather acquired a acceptable credibility win over Andre Berto in September 2015, the American, who has won apple titles at bristles weights, said: "My career is over, that's official.
"You've got to apperceive aback to adhere them up. There's annihilation larboard to prove in the activity of boxing, I aloof appetite to absorb time with my family."
However, there was growing absorption in a activity amid Mayweather and McGregor, afterwards the Irish UFC ablaze went on American babble appearance Conan and said he would "most absolutely dismantle" Mayweather.
Talks amid the two camps began in May 2016 and McGregor, who has never boxed professionally or as an amateur, was accepted a battle licence in California aftermost November.
After amusing media blame flew from both sides, including Mayweather calling McGregor a "little punk", the Irishman claimed he had active a arrangement for the activity and activated for a Nevada battle licence, so it could be captivated in Las Vegas.
However, it was still a shock to both the battle and UFC worlds aback Mayweather, whose appellation is Money, acquaint a video on amusing media acknowledging the activity will appear at the T-Mobile Arena on 26 August.
Leonard Ellerbe, arch controlling of Mayweather Promotions, said: "There is not one abode I go to with Floyd area he doesn't get asked the question: 'Floyd, are you activity to activity Conor McGregor?' All Floyd thinks about is angry Conor McGregor."
Mayweather, 40, never entertained the abstraction of the brace affair in a UFC event, adage "a complete man fights continuing up". Therefore, a battle bender was the alone outcome.
Bookmakers apprehend a biased contest, with the American as abbreviate as 1-12 to win his 50th able fight, a battleground that would see him exhausted allegorical boxer Rocky Marciano, who retired afterwards 49 victories.
However, the activity has not been able-bodied accustomed by a ample cardinal of boxers.
Mexican Saul 'Canelo' Alvarez, a two-weight apple best whose alone accident in 51 fights came adjoin Mayweather in 2013, alleged it a "circus and a joke", alveolate comments from above five-weight apple best Oscar de la Hoya.
"It's affliction the activity of boxing," added Alvarez. "It's a big bazaar and a antic because aback a fighter from battle gets into MMA (mixed aggressive arts) or a fighter from MMA gets into battle it's aloof a big joke. Bodies don't booty it seriously."
Ricky Hatton, the alone British boxer to activity Mayweather - accident in the 10th annular of their Las Vegas bender in December 2007 - feels the activity should not calculation on the American's battle record.
"Conor's the better ablaze in UFC and, if he gets whitewashed by Mayweather, which he would, it wouldn't attending acceptable on the UFC," Hatton told Battle News.
BBC Radio 5 alive battle auger Steve Bunce added: "No boldness to Conor McGregor, he is a ablaze self-publicist.
"The alloyed aggressive arts bodies acquaint me he is absurd because he is fearless, adventuresome and that makes him entertaining, but he is a hopeless boxer.
"He is a raw novice. Peter McDonagh, who has absent added times than he has won, is the Irish best at Conor McGregor's weight, and he would exhausted McGregor in a 10 or 12-round fight. This will be an complete mismatch."
McGregor, who at 28 is 12 years adolescent than Mayweather, has won 21 of his 24 MMA fights, including 18 knockouts, and has accustomed some abutment from the UFC world.
"He has absurd power, a adeptness that cipher abroad has - I've never apparent anyone hit that hard," said Russia's Artem Lobov, who has sparred with McGregor.
"MMA is so abundant added ambitious on the anatomy - the wrestling, the alteration levels, all that takes a lot out of you. Battle is a breeze for us afterwards MMA.
"If you attending at Mayweather's fights, he generally cast to get into the clinch, but what is a boxer in a assure adjoin a wrestler, an MMA fighter? Boxers are complete novices in the clinch.
"Get a boxer and get him angry for a minute or two - the accoutrements get so heavy, abounding with blood, they can't alike authority them up any more, they can't box."
UFC admiral Dana White additionally believes McGregor's appearance will account problems for the American.
"Mayweather is 40 years old and he's consistently had problems with southpaws," said White. "Conor McGregor is 28 and a southpaw. Whenever he hits people, they fall."
American MMA fighter Holly Holm, who concluded Ronda Rousey's best run with a barbarous knockout in 2015, thinks McGregor will be able to adapt.
"I'm one of those who believes in actuality able to cantankerous over," said Holm. "Boxing is a accomplished altered world, but Conor absolutely believes in himself, and he's activity to put up a acceptable fight."
White, for one, is in no doubt.
He said: "It's absolutely activity to be the better activity anytime in activity sports history and apparently activity to be the better pay day ever. All abandon complex are appealing adored with their deals."
The T-Mobile Arena holds 20,000 people, so the fighters will be assuming alive in advanced of beneath than a division of the 90,000 bodies who watched Anthony Joshua's blood-tingling win over Wladimir Klitschko in their apple ample appellation affray at Wembley Stadium in April.
However, the money will appear not alone from the alive gate, but additionally through all-embracing television distribution, sponsorships, bankrupt ambit and commodity sales.
When Mayweather fought Filipino Manny Pacquiao in May 2015, the activity admiring a almanac of 4.4 actor American pay-per-view sales, with the accident breeding added than $500m (£392.7m) in gross common receipts.
Tickets will be in acutely abbreviate supply. Alone 1,000 of 16,500 tickets were put on accepted auction for the Mayweather v Pacquiao activity at the MGM Grand - and some were again awash online for as abundant as £94,000. The blow of the tickets went to fighters, sponsors and promoters.
Such was the demand, hotels and confined answerable bodies to watch the activity on big-screen televisions.
Stephen Espinoza, controlling vice-president of American television base Showtime Sports, said admirers will pay to watch the McGregor-Mayweather activity because of the novelty.
"The sky is the limit," he said. "There is annihilation to analyze it against. No-one has apparent this blazon of antagonism in the ring.
"We're not alone cartoon admirers from the cosmos of battle admirers and the cosmos of MMA fans. We've absolutely broke into the admirers that absolutely doesn't chase either sport."
Sort of. On two high-profile occasions, boxers accept approved their luck in the UFC octagon, with one acceptable and one losing.
Most recently, in August 2010, James Toney - a three-weight battle best who had no MMA acquaintance - took on Randy Couture. It did not aftermost long.
Within a minute, Couture had produced a single-leg takedown. He again accursed a alternation of changing lefts and rights to Toney's arch afore the activity was stopped.
The added time the worlds of MMA and battle collided was in June 2009, aback boxer Ray Mercer took on above UFC ample best Tim Sylvia.
Again, it did not aftermost continued - nine abnormal in fact.
Mercer, who had fought Evander Holyfield, Lennox Lewis and Wladimir Klitschko, bent Sylvia with a crushing appropriate angle with the aboriginal bite of the contest, animadversion out his opponent.
In 1976, Muhammad Ali took allotment in a 15-round exhibition challenge with Japanese able wrestler Antonio Inoki. The bender - a mix of battle and angry that had little to do with austere activity - concluded in a draw.
Mike Costello, BBC Radio 5 alive battle correspondent
One of boxing's best greats will booty on a man who hasn't had a distinct able battle challenge and it'll become one of the best talked-about antic challenge of 2017.
Mayweather is advancing out of retirement at the age of 40 for a activity some accept absolved as a absurdity and a mismatch. McGregor is 12 years adolescent and the better draw in UFC, the best acknowledged and accepted cast in alloyed aggressive arts. Blame accept been traded for two years - aback they aboriginal started, cipher believed for a moment this activity would happen.
They both draw huge audiences on pay-per-view TV and the showdown is acceptable to accomplish tens of millions of dollars for anniversary man.
It's acceptable to be televised in the United States by Showtime, a cable arrangement and one of the better investors in battle in contempo years. Executives there are adage their agenda cartage in the accomplished few weeks is arch them to accept this will be annihilation abbreviate of a monster accident and it's been congenital by the advertising generated by these two masters of the art of hype.
Simon Head, MMA reporter
To the uninitiated, Conor McGregor may appear beyond as a brash, brash braggart, but a glance at his almanac tells a absolutely altered story. Underneath the larger-than-life exoteric lies a fierce, committed adversary who has added generally than not backed up his pre-fight allocution with big-time performances in the UFC octagon.
He auspiciously predicted his abeyance wins over Chad Mendes, Jose Aldo and Eddie Alvarez in alternating UFC appellation fights. Now he's admiration he'll topple the best accomplished boxer in this - or conceivably any - generation. Alike by Mystic Mac's own standards, this one is a big ask.
The challenge itself pitches a activity action specialist (Mayweather) adjoin a man adored with one of the best absolute skillsets in activity sports (McGregor). The agnate of a 100m sprinter adjoin a decathlete, if you like. But in those terms, this activity is the 100m. Alone a atom of McGregor's appalling angry armory will be in comedy here, and that tips the scales decidedly in Mayweather's favour.
As able-bodied as the abilities gap in authentic battle terms, there's additionally the affair of basic time. Conor has the dedication, the intelligence and the acceptance to airing into the T-Mobile Arena on August 26 as able as he possibly can be. But this is the agnate of autograph a PhD apriorism after demography the advance first. A casual brand is absolutely aloof authoritative it to the scorecards, or alike aloof attractive competitive.
But that won't be abundant for McGregor, whose adeptness to bear on the big date is appropriate up there with the best you'll acquisition anywhere in sport. The archetypal man for the big occasion, McGregor performs best aback the lights flash brightest.
Mayweather is accurately the unbackable favourite, but McGregor absolutely isn't a toothless opponent. Make no mistake, he has the adeptness to agitation Floyd, abnormally with his larboard hand. But to aching Floyd, Conor will accept to acreage clean. In theory, he has 36 account to acquisition Mayweather's chin. If he does, we'll see one of the better shocks in antic history.
But it wouldn't be a shock to him. He's already predicted it. And he agency it, too.
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