Floyd Mayweather Jr. wasn’t just the highest-paid athlete on Forbes’ 2012 list of the highest-paid athletes, he out-earned the next highest athlete, Manny Pacquiao, by over $23 million. Tiger Woods, who has held the top position since 2001, was $25 million behind Mayweather. Now there’s every reason to believe Mayweather will hold his ground at the top for years to come with the announcement that Mayweather is jumping HBO’s ship to join Showtime in a deal the network says has the potential to be the richest deal in history for an individual athlete.

CBS-owned Showtime has announced a new deal with Mayweather for up to 6 fights over the next 30 months. If all of those fights are completed, and Mayweather draws his usual average of 1 million PPV buys, Showtime says Mayweather will make history financially.

The relationship is anything but one-sided. Showtime executive vice president and general manager Stephen Espinoza says having Mayweather on the network is a slam dunk.

“Floyd [Mayweather] is one of the most compelling and entertaining personalities in all of sports, plus he’s the top active boxer in the sport today. You don’t normally get elite performance, charisma and personality all in one package.”

The Mayweather deal is also a big step toward fulfilling Espinoza’s goals at Showtime.

“As soon as I took the job here at Showtime 14 months ago one of my goals was to be in the big event business as soon as possible. When you’re talking about big event business, the current landscape means Pacquiao or Mayweather. While I didn’t necessarily want to be in PPV as a goal, I did want to be in the Pacquiao or Mayweather business.”

Between the two, Espinoza knew he wanted Mayweather, so zeroed in on his target, making his first pitch just four weeks into his new job. Unfortunately for Espinoza and Showtime, Mayweather opted to stay with HBO.

“I marshaled the forces and made another pitch when he announced this May fight,” said Espinoza, referring Mayweather’s upcoming fight on May 4 against Robert “The Ghost” Guerrero. “At that point I was able to make a more aggressive offer.”

Showtime has declined to share the terms of the agreement other than to mention it’s potentially record-breaking, but Espinoza put it simply, saying, “I made him an offer he couldn’t refuse.”

The deal is important for Mayweather, who made all of his estimated $85 million on Forbes’ 2012 highest-paid athletes list inside the ring. Other top-earners generate as much or more from endorsements as they do from salary or performance-related compensation. For example, in 2012 Woods generated $55 million of his total $59.4 million earnings from endorsements.

However, experts say the lack of endorsements for Mayweather aren’t as much a reflection of his personality and highly publicized run-ins with the law as an indication of how the sports marketing world views boxing.

“People are interested in the spectacle of the pay-per-view , but at the end of the day, it’s not a sport they follow day to day,” says Marc Ippolito, president and general counsel of Burns Entertainment & Sports Marketing, Inc.

“The overall interest in comparison to the other sports is not the same, so from a brand perspective they don’t see as much value. Some of them fight only once a year. They’re not there every week or even every month.”

Judging by his 2011-2012 haul, Mayweather doesn’t need endorsements. His $85 million he earned were from two fights, the combined total of which was under an hour: a fight in which he knocked out Victor Ortiz in September 2011 and a unanimous-decision win against Miquel Cotto in May 2012 (Forbes measures athlete earnings from June to June).