Floyd Mayweather Jr finalised a deal to fight Sugar Shane Mosley on May 1 in a welterweight bout at the MGM Grand Garden in Las Vegas.
Mayweather (40-0, 25 KOs) agreed to the bout last week, but formally signed the contract on Wednesday for his second fight back from a brief retirement.
"This one is definitely for the fans, as I wasn't going to waste anyone's time with a meaningless tune-up bout and asked to fight Shane immediately," Mayweather said. "I have said ever since I came back to the sport that I only wanted to fight the best. I think Shane is one of the best, but come May 1, he still won't be great enough to beat me."
Mayweather and Mosley have agreed to Olympic-style drug testing for their fight, saying they hope to set a new standard for safety in boxing. Mosley has acknowledged using steroids before a victory over Oscar De La Hoya in 2003, but claims he did so inadvertently through a coach who had connections with the BALCO lab.
"I'm real disappointed and real angry to be linked to juicing and steroids, because that's just not me," Mosley said. "I don't need to do that stuff. I like the testing for this fight. I want it because I want to prove that everything I've done is all me, and not about steroids."
Mosley, (46-5, 39 KOs) the 38-year-old WBA welterweight super champion, has been vocal about his desire to meet Mayweather ever since Mayweather celebrated his return last September with a one-sided victory over Juan Manuel Marquez. Mosley jumped into the ring after Mayweather's win and taunted the fighter.
Mosley's only loss since late 2004 was a narrow decision to Miguel Cotto in November 2007. He has fought just twice since then, stopping Ricardo Mayorga and Antonio Margarito.
Mayweather should have the services of Roger Mayweather, his uncle and long-time trainer. Roger has a June 1 trial date in Las Vegas on several serious charges related to accusations of beating and choking a female boxer last summer.