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Jae C. Hong/Associated Press

Few believed that Floyd Mayweather Jr. was serious when he stated he was done with boxing after his 2015 match with Andre Berto. And why would they? Even at 38 years old and even with 49 fights on his pro boxing record, Money was still remarkably sharp in the ring.

His defense was still nearly impenetrable. His right hand was still nimble enough to reliably find its way to opponents' chins. And of course, there were still lucrative contests to be made.

Getting Mayweather back into the ring was always a matter of finding the right opponent and payday. Ironically, it took somebody from outside the ring to fit that bill. While the undefeated pugilist was enjoying life away from competition, a legitimate threat to his "King of Pay-Per-View" throne rose up in the realm of MMA. And rose up remarkably quickly.

Irish featherweight Conor McGregor exploded into the UFC in 2013 and was firmly established as one of the company's hottest commodities by the end of 2014. In 2015, he helped propel the UFC to its most successful year ever with his bouts against Chad Mendes and Jose Aldo. He was a snowball rolling downhill when the calendar turned to 2016, and he proved as much by breaking the UFC's buyrate record at UFC 196, doing so again at UFC 202 and capping off the year by becoming the first man to hold two UFC titles simultaneously.

That rise to the top, however, was so quick that he left the UFC's stratosphere entirely.

No contender had anything to offer to his bottom line. Hunting a third UFC title probably wouldn't have been much better. There was no big opportunity just on the horizon.

Sure, McGregor could have stayed the course. A fight with any of the no-namers that make up the UFC's rankings was still an all-but-guaranteed one-million-buy card. Booming business, however, has defined McGregor's career, and quietly plateauing isn't really his modus operandi.

Already high up on the mountain, McGregor set his sights for the peak, and Mayweather was happy to greet him.

For Mayweather, McGregor is just easy money; an out-of-his-depth opponent who just so happens to have a massive fanbase with lots of disposable income. For McGregor, this is an opportunity to take Money's spot as the kingpin of combat sports. On August 26, Mayweather will put his past on the line against McGregor's future in what will likely go down as one of the biggest contests in combat sports history.