Floyd Mayweather totally out-classed Conor McGregor

Floyd Mayweather Jr. will retire a perfect 50-0 -- and Conor McGregor made him work for it.

McGregor's first boxing match was a heckuva show -- the 29-year-old mixed martial-arts superstar acquitted himself beautifully on Saturday night in Las Vegas, hitting Mayweather more than the champ is used to -- but one of the 40-year-old Mayweather's powerful right-hand jabs round dazed the Irishman badly in the 9th, and Mayweather quickly took advantage.

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Mayweather pressed the attack straightaway in the 10th; McGregor, looking totally gassed, had nothing left, and as Floyd's punches began landing more fiercely, veteran referee Robert Byrd called it. Mayweather would win his last fight in a knockout.

McGregor went toe-to-toe with Mayweather in early rounds, landing straight-ahead jabs, counterpunching well and overall being more active and aggressive than his veteran opponent. Mayweather kept ducking, weaving, and jumping back alright -- he's the most elusive boxer who ever lived, after all -- but he looked oddly flat-footed, and it began to look like McGregor had a chance.

The newbie McGregor was admirably composed and prepared, though he was throwing borderline sketchy "hammer" punches to the back of Mayweather's head as he dipped at the waist, a legal punch in MMA but a no-no in boxing. The southpaw McGregor also always kept his right hand up in Mayweather's face, a tactic that clearly irritated Mayweather, who kept batting it away to get an angle. But it was McGregor who was finding his way through Mayweather's infamous defenses, and by the 5th round, Mayweather looked frustrated.

Mayweather abandoned his retreating style in the 6th and began to take control, splashing McGregor's front with crafty counters and combos. Then came the 8th -- one of the sluggiest, most entertaining rounds of boxing that Floyd "Money" Mayweather has ever been a part of. McGregor stuck Mayweather with a stiff jab early, but Mayweather came slashing back with vicious hooks and jabs; he'd chosen his moment to go for the KO.

Then in the 9th, McGregor turned the tables with a devastating (and possibly too low) body shot that looked to hurt Mayweather, badly. Instead he flurried back, including a right jab to the flat of McGregor's face -- a perfect punch. That would do it. McGregor dazed and fading, Mayweather went in for the kill, but the bell rang out the 9th.

The  10th wouldn't last long; Mayweather went right to work, and after McGregor took four heavy hands to the head, the fight was over.

Mayweather, who last fought two years ago in a unanimous decision win against Manny Pacquiao, came out of retirement for yet another $100 million guaranteed purse, and will make more than $200 million after his piece of the pay-per-view comes in from Showtime. McGregor's purse is $30 million -- and while that's significantly less than Mayweather, it's far more than he's ever made for a UFC fight. He was expected to walk away with something in excess of $100 million.

"This was my last fight," Mayweather said. He'll retire a perfect 50-0, and goes out with one of the most entertaining performances of his storied career.