Floyd Mayweather Jr., set to exit his year-plus retirement to face Juan Manuel Marquez on July 18 at the MGM Grand in Las Vegas, suffered a rib injury in training late last week, forcing him to postpone the welterweight fight on Sunday.
"I am extremely disappointed that this fight has to be postponed," Mayweather (39-0, 25 KOs) said in a statement. "I was training very hard and looking forward to getting back in the ring."
Marquez (50-4-1, 37 KOs) said in a statement from his training camp in Mexico that he was also disappointed.
"I will remain focused, in shape and ready to fight whenever the fight is rescheduled for," the lightweight champion said. Marquez will receive a minimum $4 million payday for the fight.
Golden Boy CEO Richard Schaefer, one of the promoters of the fight, told ESPN.com that Mayweather was injured late last week but tried to work through the injury but was unable to.
"It was very painful," Schaefer said. "I don't know the extent of it is, but he went to go see a doctor and he is in tremendous pain, so we have no choice but to postpone the fight. He obviously knows how dangerous of an opponent Marquez is and he wants to make sure he is in the best shape possible.
"We will find out more in the next few days as he goes and sees the doctor again. He definitely wants to fight and he wants to fight Marquez. He knows it's a big fight. But at the same time, he knows he has to be in the best shape. He said, 'Let's see what dates are available and let's postpone it.' We want to make sure he is OK. Like he said when he came back at the press conference, this isn't just for one fight. He wants to make sure he is perfectly healthy and ready to go."
Rescheduling the fight will be a difficult task and largely depends on when Mayweather is available. If Mayweather is healthy, a likely date is Sept. 19, which is the weekend of Mexican Independence Day and a weekend where there is traditionally a major fight involving a Mexican boxer. Marquez is regarded as Mexico's No. 1 active fighter.
"I've been on the phone talking to HBO, talking to the MGM Grand, talking to our sponsors, and my talking to my team about all of the issues," Schaefer said. "The new date will depend on doctor's orders. Will it be a month later? Two months later? We don't know. He needs to heal. But I was a told its was probably a cartilage thing, not a broken rib or anything."
Mayweather officially ended his retirement on May 2 when he announced he would fight Marquez. They were scheduled to fight at a catch-weight of 144 pounds, more than Marquez has ever fought and the lightest weight for Mayweather since 2005.
Mayweather hasn't boxed since knocking out Ricky Hatton in December 2007. The former five-division champ was slated to fight a rematch with Oscar De La Hoya but instead abruptly retired last June, turning his attention to show business.
Dan Rafael covers boxing for ESPN.com. Information from The Associated Press was used in this report.