By Keith Idec

NEW YORK – If the almost unfathomable becomes reality next month, and Conor McGregor upsets Floyd Mayweather Jr., Mayweather won’t work from his usual position of negotiating strength if he wants a rematch.

Showtime Sports’ Stephen Espinoza confirmed Thursday night before a press conference at Barclays Center that there is not a rematch clause in the contracts for their August 26 boxing match at T-Mobile Arena in Las Vegas (Showtime Pay-Per-View; $99.95 in HD).

“There is no rematch clause,” said Espinoza, executive vice president and general manager for Showtime Sports. “There was talk of it early on. Neither side had any particular interest.”

The 40-year-old Mayweather has repeatedly stated that the McGregor match will be the last of his legendary career. The former five-division champion has come out of retirement twice, though, and seemingly would want to avenge what would be his first defeat since suffering a controversial loss at the 1996 Summer Olympics in Atlanta.

The enormous amount of revenue this pay-per-view event is expected to generate also could make Mayweather and McGregor seriously consider a rematch if the UFC superstar somehow wins. Mayweather is slightly more than a 5-1 favorite against McGregor, a powerful southpaw who is 11 years younger than Mayweather, yet a novice boxer.

Mayweather (49-0, 26 KOs) has participated in two rematches during his 20-year pro boxing career. The Grand Rapids, Michigan, native defeated Jose Luis Castillo by unanimous decision in December 2002 and beat Marcos Maidana by unanimous decision in September 2014.

McGregor (21-3, 18 KOs in MMA) beat Nate Diaz by majority decision last August 20 in the lone rematch of his mixed martial arts career. Diaz upset McGregor by third-round submission in their first fight, five months earlier.

Both bouts against Diaz were contested at the MMA welterweight limit of 170 pounds, 25 above the MMA featherweight limit at which McGregor had been competing.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.