Five reasons why UFC champion Conor McGregor could beat Floyd Mayweather

UFC lightweight champion Conor McGregor will be the underdog when he squares off with undefeated boxing superstar Floyd Mayweather Jr. on Aug. 26 at T-Mobile Arena in Las Vegas.

And that is the way it should be. McGregor, after all, has never had a professional boxing match, while Mayweather carries a 49-0 record into the fight, which will be broadcast on pay-per-view television. If Mayweather was fighting under mixed martial arts rules, he'd be just as heavy an underdog to McGregor.

We're not going to tell you to put money down on the 'dog in a fight, which is such an on-paper mismatch, but if you were going to try convincing yourself that McGregor could pull off a Super Bowl III-like upset, here are five reasons:

1. Size: The matchup is being conducted at 154 pounds. Mayweather started his career at 130 pounds, and while he's fought as high as 154, he conducted the bulk of his prime at welterweight (147 pounds). McGregor, meanwhile, has alternated between featherweight (145 pounds; MMA and boxing weight classes differ in size) and lightweight (155) for the bulk of his career. In 2016, in his two biggest career MMA fights, McGregor fought Nate Diaz at welterweight (170 pounds in MMA). McGregor also made fun of Mayweather during their promotional tour in July for wearing what appeared to be lifts in his sneakers to make him appear to be McGregor's size. With a day to rehydrate following weigh-ins and bell time, it is highly likely McGregor will have a significant size advantage by the time they step into the ring.

2. A crushing left hand: Mayweather's a conventional fighter and has had his share of trouble with left-handers over his career. Notably, early on, both Jose Luis Castillo and Zab Judah gave Mayweather fits, although he made adjustments on the fly and earned the victory. McGregor, meanwhile, has absolutely crumpled opponents in the Octagon while wearing four-ounce gloves. Jose Aldo, featherweight champion for six years, saw his reign end in 13 seconds when he walked straight into a McGregor left. Eddie Alvarez, a hard-nosed lightweight champion in several organizations, had no answer for McGregor at UFC 205 in dropping the title. Landing on Mayweather is easier said than done, but the Irishman has already shown he has the power: McGregor's promoter, Dana White, leaked footage of McGregor rocking former world champion Paulie Malignaggi with a wicked left and then dropping him during a recent sparring session.

3. Age and inactivity: McGregor is just coming into the prime of his fighting career, having turned 28 last month. Mayweather, meanwhile, turned 40 in February. He hasn't fought since Sept. 12, 2015, when he won a unanimous decision over Andre Berto, then retired with a 49-0 record. When fighters drop off, it tends to happen in a hurry. Ring rust is a real thing. There's no guarantee, now that he's on the other side of 40, that Mayweather will show up after a two-year break and suddenly return to peak form.

4. Overconfidence: Maybe Mayweather will believe the hype. Maybe he truly believes that all he has to do is show up and the rest will take care of itself. Maybe he'll abandon his trademark patience and go headhunting, looking to defend the honor of boxing against an MMA intruder, and leave himself open for a counter knockout. McGregor has made a career out of being underestimated, and Mayweather would make for his biggest scalp.

5. Self-belief: Just five years ago, McGregor was on the public dole in Ireland, as the Dublin native was trying to make ends meet in one of Dublin's rougher parts of town. He went from there to UFC success, winning the featherweight title against a dominant longtime champion in Aldo, who came into their December 2015 bout with an unbeatable aura. When McGregor was submitted by Diaz at welterweight in a short-notice bout for his only UFC loss, McGregor insisted upon having an immediate rematch, also at welterweight, even though Diaz was the larger man. And McGregor won the rematch. He then insisted he was going to become the first simultaneous, two-weight-class champion in the UFC's 24-year history, and went out and knocked out Alvarez to win the lightweight belt while still holding featherweight gold (which he has since vacated). McGregor also willed the Mayweather fight into existence, getting the UFC to alter policy on fighters taking outside bouts and making "McGregor Promotions" a co-promoter. When McGregor aims high, he usually hits, and that's as good a reason as any to believe he can win the fight.