Conor McGregor may have as many as 20 pounds on Floyd Mayweather on fight night

Conor McGregor stepped on the scale at 153 pounds at the weigh-in Friday, just a little heavier than the 149 1/2 pounds for Floyd Mayweather Jr. Both made it under the 154-pound limit, but on fight night McGregor may be as many as 20 pounds heavier than his opponent.

“A lot bigger than him,” McGregor answered when Showtime’s Jim Gray asked how much he’ll weigh Saturday. “I’d say close to 170 [pounds].”

That’s not surprising and is similar to the weight he has fought at in the UFC. According to MMA Fighting’s Ariel Helwani, McGregor showed up to T-Mobile Arena on Saturday night around that weight.

This isn’t unexpected and an advantage McGregor expected to have all along. Last week, his longtime coach John Kavanagh also predicted the fighter would approach 170 pounds on Saturday.

"He'll be up close to that come fight night,” Kavanagh said. “What was he, 168 pounds for Diaz II? What did he say in that clip? He's a 170-pound Irish gorilla. He'll be up close to that number."

For Mayweather, adding on pounds in the next 24 hours is unlikely. If he hoped to be bigger, the 49-0 boxer likely would’ve came in closer to the 154-pound limit like McGregor. Instead, he was nearly five pounds under that mark.

Why does McGregor add weight after weighing in?

Extreme weight cuts are a controversial, but common part of mixed martial arts. Fighters attempt to lose as much weight as possible in the days leading up to the fight, rarely come in more than a pound below the limit, and then bulk back up in the final day before entering the cage.

It’s a dangerous norm in the sport that has caused health issues for many fighters and has been the focus of many athletic commissions hoping to make MMA safer.

McGregor is among the best at cutting weight. Despite walking around and training at over 160 pounds, he won the UFC’s 145-pound featherweight championship after cutting scary amounts for each fight.

This was McGregor prior to his last fight at 145 pounds:

Gary A. Vasquez-USA TODAY Sports

Compare that to McGregor prior to a fight against Nate Diaz three months later when he weighed in at 168 pounds:

Mark J. Rebilas-USA TODAY Sports

But why does MMA have such extreme weight cuts, while boxing typically features fighters stepping on the scales at the same weight as fight night?

McGregor’s nutritionist George Lockhart — who helped him ace the 154-pound limit Friday — explained in an interview with MMA Fighting’s Ariel Helwani last month.

“Boxing is a lot different,” Lockhart said. “A lot of people are like ‘George, you need to get into the boxing world,’ but a lot of these guys just walk right in on weight. Nobody’s hanging on you, nobody’s trying to take you down, so that weight doesn’t really have as much of a factor in boxing.”

While size and strength are important in MMA to prevent getting out-wrestled and out-grappled, it isn’t as important in boxing — a sport where speed and quickness take precedence.

Does McGregor’s size advantage actually matter?

Mayweather doesn’t think so.

When asked by Jim Gray why he chose to weigh only 149.5 pounds for a fight set at 154 pounds, he dismissed the difference as a non-factor.

"Weight doesn't win fights,” Mayweather said. “Fighting wins fights."

But it is a factor. McGregor will likely hold the biggest size advantage that Mayweather has ever faced. There are upsides and downsides for the weight discrepancy for both fighters, though.

McGregor’s best chance at pulling off the upset victory would be to land his left hand on the chin of Mayweather. That same left hand won McGregor multiple fights in the UFC and is the most dangerous weapon he brings to the fight Saturday.

With a 20-pound advantage and undersized gloves for the weight class, McGregor has an even higher chance of bringing fight-ending power if he manages to land that left hand cleanly.

But Mayweather’s gameplan was never to land a power shot anyway. His style has always been as a defensive boxer who wears opponents down with his speed, evasiveness and technical skill.

While he has promised that the fight won’t go the distance, the most realistic way Mayweather wins without the judges rendering a decision is if he overwhelms McGregor with speed that tugs at the Irish MMA star’s endurance.

With that strategy in mind, being smaller and faster could play to Mayweather’s advantage too and allow him to pick apart the body of McGregor.

McGregor is aiming to win with his power. Mayweather is aiming to win with his speed. An extra 20 pounds for McGregor furthers that narrative Saturday.