Floyd Mayweather Jr. versus Manny Pacquiao II? Not so fast. Mayweather reneged on his promise of granting Pacquiao a rematch, calling him a "sore loser" and a "coward" for citing an injury as the reason he lost May 2.

Mayweather (48-0) apparently had been ready to put off his retirement in September in order to grant Pacquiao plenty of time to recover from surgery for a rematch, but not anymore. The undefeated champion has had a change of heart since telling an ESPN commentator on Tuesday he would be willing to fight Pacquiao again sometime next year.

"Did I text (ESPN commentator) Stephen A. Smith and say I will fight him again? Yeah, but I change my mind. At this particular time, no, because he's a sore loser and he's a coward," Mayweather said this week in a taped interview set to air this weekend, according to ESPN. "... If you lost, accept the loss and say, 'Mayweather, you were the better fighter."

Mayweather indicated the reason he changed his mind was because Pacquiao, instead of accepting the loss like a professional, told reporters immediately after the fight he had been hampered by a shoulder injury.

"I'm not going to buy into the bulls--- ... and I don't want the public to buy into the bulls---," Mayweather said. "He lost. He knows he lost. I lost a lot of respect for him after all this."

Pacquiao, who lost by a unanimous decision Saturday, said he suffered a right shoulder injury while training and had not been allowed to take an anti-inflammatory injection prior to the fight. Although Pacquiao never explicitly blamed the loss on his injury, he did say he was less than 100 percent healthy for the fight.

He underwent arthroscopic surgery on Wednesday to repair a "significant tear" in his rotator cuff, according to his surgeon.

For Mayweather's part, though, he believes the injury was just an excuse. When asked if he noticed a problem with Pacquiao's right shoulder during the fight, Mayweather answered: "Absolutely Not. He was fast. His left hand was fast. His right hand was fast, and he was throwing them both fast and strong. Excuses, excuses."

Mayweather said he won't fight Pacquiao again, but it's also possible his claim is just a PR move to hype up Mayweather-Pacquiao II. Mayweather has one fight left on his contract and has said he will retire in September. Mayweather-Pacquiao I was boring, but given the state of boxing, fighting Pacquiao again - especially after he went public with his injury - stands to make Mayweather the most money if he wants one last humungous payday before hanging up his gloves.

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What happened with the whole Pacquiao injury ordeal?

Pacquiao said he suffered a shoulder injury while training, but he and his camp failed to disclose the injury in a form given to the Nevada Athletic Commission prior to Friday's weigh-in. When Pacquiao asked permission to receive an anti-inflammatory injection on the night of the fight, the Nevada boxing officials said no.

"It's not just the fact he didn't fill out the question completely, it was that he wasn't honest and they didn't tell us a month ago when he had the shoulder injury," said Nevada Athletic Commission executive director Bob Bennett, according to ESPN. "They're not obligated to, but two hours before the fight they wanted a shot that's a painkiller, in essence. That put us in a very precarious position."

Pacquiao's camp said Monday it had told the U.S. Anti-Doping Agency about his injury, but the agency is a non-governmental organization that only has the power to drug test the fighters. Pacquiao needed permission for the injection from the Nevada boxing officials, who declined to give it hours before the fight because this was the first they heard about the injury.

"Either (Pacquiao's camp) made a terrible mistake to not follow the rules or they were trying not to give information to the other side," said USADA head Travis Tygart. "I'm not sure there's a middle ground."