The official announcement of the improbable pairing of Conor McGregor and Floyd Mayweather was only hours old when UFC president Dana White offered his thoughts on the UFC lightweight champion’s chances in a ring with the best boxer of the last 20 years.

“Floyd, traditionally, if you want to say there’s ever been a kink in the armor with that kid, it’s with southpaws, and Conor McGregor is an absolute knockout artist,” he said during a conference call. “When he hits you, you go.”

Southpaws. It is one of the few factors McGregor supporters have pointed to as a potential area of advantage for the longtime mixed martial artist as he wades into the realm of a 49-0 master. Never mind that it can hardly be considered as anything more than opinion.

As best anyone can tell, the pervasive belief that Mayweather struggles with southpaws was born in a five-fight stretch from 2004 to 2006 during which he fought three left-handers. Of that group, both Zab Judah and DeMarcus Corley both drilled Mayweather with shots in a way that has rarely happened before or since.

Corley hurt Mayweather in the third round, then staggered him with a right in the fourth. Judah landed several hard punches against Mayweather, including a right hook that was controversially ruled a slip, as well as a thunderous fourth-round barrage.

Because Mayweather is hit clean so rarely, those strikes have grown in both lore and historical significance. Conversely, their importance has become magnified to outsized proportions; their rarity has fed their value.

“Floyd’s fought some of the greatest left-handed fighters in the world and not only didn’t they beat him, they had trouble touching him.”

In truth though, those shots, however effective in the moment, were blips in the road for a rapidly improving fighter. Two punches aside, Mayweather routed Corley in a lopsided unanimous decision that included two knockdowns of his own. Against Judah, Mayweather faced his worst danger in the fourth, then rebounded by winning every remaining round.

“Floyd’s fought some of the greatest left-handed fighters in the world and not only didn’t they beat him, they had trouble touching him,” former two-division boxing champion Vinny Paz told MMA Fighting. “Conor is a really good MMA guy, but in the boxing arena, he doesn’t have great skills. He’s going to be looking for that big punch, and Floyd never gets hit by that. Only one, maybe two times, and when he does, he gets himself back together. Floyd is the only one who can make it look like a close fight because his defensive skills are so incredible.”

That’s not to say Mayweather never had a problem with southpaws. Holes are often unknown even to the fighter until they are exploited, at which point it’s the responsibility of the athlete and his camp to address them.

Mayweather has long been lauded for his fight IQ and his ability to input information and make adjustments on the fly. And that’s during the course of a frenetic fight. If that’s the case, it only stands to reason that whatever holes he might have had over a decade ago have long since been addressed.

“I believe at the beginning he had a lot of difficulties when it comes to southpaws,” Mayweather’s last opponent Andre Berto said in a recent appearance on The MMA Hour. “But within the last few years, he’s definitely dialed in. He’s worked the southpaw stance and picked the situation apart. I don’t think it’s going to be as troublesome as everybody believes. He has a tremendous right hand and that’s always a key weapon when dealing with a southpaw. Lead right hand and left hook. He’s shown that in the Robert Guerrero fight, the Victor Ortiz fight and the [Manny] Pacquiao fight, that he has the laser position on that right hand left hook and is able to get out of the way.”

Angelo Reyes, a boxing trainer who has coached MMA fighters including Frank Mir and Brandon Vera, agrees.

“Anyone who says Floyd struggles against southpaws, that’s the most ridiculous statement I’ve ever heard in my life,” said Reyes, who learned his trade under legendary trainer Freddie Roach. “If you’re 49-0 and undefeated and have never lost to a lefty, do you have a problem? You know who’s the guy who tested that theory? His name is Manny Pacquiao, and he’s a first-ballot Hall of Famer. This is kind of like when [Michael] Jordan was great, and everyone was constantly looking for an Achilles Heel. That’s not it for Floyd.”

Boxing is a sport of angles and positioning, and part of Mayweather’s genius is in always being in the most advantageous position.

That comes from thousands of hours spent refining the minutiae of the craft, sometimes changing foot position or body lean by mere millimeters in order to set up the proper defense and prepare an immediate counter.

For Mayweather, this played out as his career progressed and he altered his style to address constant and nagging hand injuries that limited his punching power. While one element of his game downshifted, his defensive abilities improved to the point it’s sometimes comedic to watch opponents try to hit him. That’s held true against both orthodox fighters and southpaws, even against foes of advancing skill levels.

Corley, Mayweather’s first meaningful southpaw opponent back in May 2004, had arguably more success against him than any left-hander, landing 150 of 657 punches (23 percent). But things trended immediately downward from there. Mitchell, en route to getting TKO’d, could land just 31 of 274 (11.3 percent) of his strikes. Judah connected on only 89 of 485 strikes (18 percent).

His three most recent southpaw opponents (Victor Ortiz, Robert Guerrero and Pacquiao) have hardly faired better, landing just 220 of 1,158 punches — a woeful 19 percent clip.

And these are lifelong boxers.

“That’s a battle Conor can’t win. He doesn’t have the coaches, he doesn’t have the sparring partners, he doesn’t have the experience.”

“Boxing is about positioning,” Reyes said. “It’s just like jiu-jitsu. The Pacquiao-Mayweather fight was a positioning battle. Boxing is when you hit me, and when I try to hit back, you’re not there. That’s the highest level. That’s where Floyd is at. Even though he’s older and hasn’t been in the ring all this time, tell me the fight that position-wise, Conor is in best position when it comes to hands. The Nate Diaz fight shows you that he can be hit, and not only that, he doesn’t know how to get out of the way. Because he doesn’t understand the positioning battles that Manny and Floyd were having. That’s a battle Conor can’t win. He doesn’t have the coaches, he doesn’t have the sparring partners, he doesn’t have the experience.”

That’s not to say McGregor can’t build some momentum.

A commonly predicted scenario is one in which Mayweather goes defensive the first two rounds to gauge McGregor’s speed and timing before opening up his offense, possibly giving away a round or two in the process.

The shift from 10-ounce gloves to eight-ounce gloves, recently approved by the Nevada athletic commission, is also seen by some as advantageous to McGregor due to his MMA experience using small gloves, never mind the fact that Mayweather has fought almost the entirety of his career in the eight-ouncers.

Still, southpaw or not, the outcome seems assured to most insiders.

“That [eight-ounce] glove is full of pain, but there’s no f’n way in God’s green world that Conor McGregor can beat Floyd Mayweather,” said Paz, who had his life story told in the 2016 movie Bleed For This. “He’s got to get lucky, he’s got to press him, to be quick and outfox him to get him with a good shot. But I can’t see that happening. Floyd has great defensive moves, great eye and hand control. He’s an incredible boxer. People talk about his defense, but he can do everything.”

"Conor’s greatest weapon is his 100 percent unicorn belief that with his weird-ass style, he’s going to catch Floyd in four rounds or less,” Reyes added. “And he really believes it. But Conor needed time [to prepare] and he didn’t get it, so all he has is that faith. Are there openings to Floyd? Yeah. But who’s going to exploit it? Not Conor McGregor, I’ll tell you that sh*t. It won’t be him. If Manny Pacquiao couldn’t do it, it won’t be him.”

One thing is for sure: while McGregor has beaten the odds repeatedly during the course of his fight career, this marks his most impossible challenge.

The crowds may be firmly in his camp, but history is not. McGregor may be mystical, but Mayweather is mythical, and as he’ll tell you, not in the fictitious, stuggles-against-southpaws kind of way. In the most meaningful way, one that can be shut down to debate, no matter the approach.

“Last time I checked,” Mayweather said, “I was undefeated.”