Floyd Mayweather Jr. has long maintained that he is clean and drug-free but a recent report from Thomas Hauser of SB Nation says otherwise.

According to the report, Mayweather received an illegal dose of IV to fend off dehydration before his May 2 match with Filipino boxer Manny Pacquiao. There was evidence reportedly found by the United States Anti-Doping Agency (USADA) after the weigh-ins, although the findings remain unclear.

Recall that before the Mayweather-Pacquiao tiff ever got underway, the Filipino boxer had wanted a $5 million fine imposed on the fighter found positive for using performance-enhancing drugs (PEDs). And as everyone knows, Mayweather shot down that stipulation which comes a bit strange considering that Mayweather and his camp had always made accusations that Pacquiao could be using PEDs.

After news broke out, Mayweather maintained he was clean. In fact, he singles out that it was he who was behind the elevation of the level of drug testing in boxing, raising the awareness of drug use.

"As already confirmed by the USADA Statement, I did not commit any violations of the Nevada or USADA drug testing guidelines," Mayweather said via Boxing Mad Magazine. "I follow and have always followed the rules of Nevada and USADA, the gold standard of drug testing," he added.

Mayweather made the statements after USADA made its own statement on the matter. Part of that statement says:

"As was already publicly reported in May of this year by the Nevada State Athletic Commission (NSAC), Mr. Mayweather applied for and was granted a Therapeutic Use Exemption (TUE) by USADA for an IV infusion of saline and vitamins that was administered prior to his May 2 fight against Pacquiao. Mr. Mayweather's use of the IV was not prohibited under the NSAC rules at that time and would not be a violation of the NSAC rules today."

The full statement of USADA can be read here.

As for Pacquiao, he wants Mayweather punished if he did take in that banned substance as well as a rematch.

"If needed, the NSAC should impose the appropriate sanction to sustain its credibility and to show the world they did not give preferential treatment to the Mayweather camp," says Pacquiao via Yahoo Sports.

And with that comes the obvious, Pacquiao asking a rematch since he was treated unfairly. Recall that prior to the match, the body refused to let Pacquiao take USADA-approved painkillers for the fight.

This development casts a dark shadow as Mayweather prepares to take in what he says is his last fight in the ring against Andre Berto this coming weekend at the MGM Grand Garden in Las Vegas.

Another win by Mayweather places him on equal footing with boxing great Rocky Marciano at 49–0. What happens next is anyone's guess.