Floyd Mayweather, who has long been a proponent of drug testing in boxing, reportedly violated World Anti-Doping Agency guidelines prior to his May 2 mega-fight with Manny Pacquiao. According to an extensive report by Thomas Hauser of SB Nation, Mayweather was administered an illegal IV on the night before he defeated Pacquiao by unanimous decision at the MGM Grand Garden Arena in Las Vegas.

The violation was discovered when collection agents for the United States Anti-Doping Agency visited Mayweather’s Las Vegas home on the Friday night before the fight. Mayweather’s medical team admitted to giving the boxer an IV consisting of two mixes - a mixture of saline and multi vitamins and a second mixture of saline and Vitamin C. While Mayweather’s team said the IV was administered to combat dehydration, doing so at any time is not in line with USADA standards.

The IV itself might not be a performance-enhancing drug, but it could potentially be used to mask other substances that are present in a boxer’s body. The USADA gave Mayweather an exemption three weeks after the fight, but Nevada State Athletic Commission executive director Bob Bennett said only the commission has the power to do so. The NSAC wasn’t notified of the exemption until after it was given.

The USADA has said that Mayweather followed protocol in disclosing information about the IV, and Mayweather released a statement of his own, reiterating that he doesn’t take PEDs.

"Let's not forget that I was the one six years ago who insisted on elevating the level of drug testing for all my fights," Mayweather said. "As a result, there is more drug testing and awareness of its importance in the sport of boxing today than ever before. I am very proud to be a clean athlete and will continue to champion the cause."

Pacquiao was informed shortly after Mayweather was granted the exemption. While Mayweather was allowed to use the IV, Pacquiao was not given permission to use Toradol, a legal painkiller, on the night of the fight. Pacquiao was battling a shoulder injury that eventually forced him to have surgery, but the NSAC denied his request because he hadn’t previously disclosed the injury.

Mayweather has been very outspoken about performance-enhancing drugs, especially in regards to Pacquiao. It looked like the boxers would fight in 2010, but a deal was never reached because Pacquiao wouldn’t agree to the drug-testing that Mayweather proposed. Mayweather even insinuated that Pacquiao had used PEDs, which led to Pacquiao suing his eventual opponent.

Mayweather was given the exemption nearly four months ago, but the report didn’t surface until just a few days before the boxer’s next fight. The 38-year-old is set to face Andre Berto on Saturday in what Mayweather insists will be the final bout of his career.

Much of the boxing world was disappointed when Mayweather pegged Berto to be his opponent, and this latest controversy is garnering as much attention as the upcoming fight. The MGM Grand is having troubling selling tickets, and the hotel has offered deals as they try to sell out the event.