TOPSHOT - Boxer Floyd Mayweather Jr. (L) and MMA figher Connor Mcgregor pose during their weigh- in on August 25, 2017, in Las Vegas, Nevada.  
Mayweather, the 40-year-old undefeated former welterweight boxing champion, will face McGregor, a star of mixed martial arts' Ultimate Fighting Championship, in a 12-round contest under boxing rules on August 26. / AFP PHOTO / John GURZINSKI        (Photo credit should read JOHN GURZINSKI/AFP/Getty Images)