Floyd Mayweather Jr., boxing's pound-for-pound king and long an advocate of strict, pre-fight drug testing, is in some hot water ahead of his Saturday night showdown with Andre Berto. Mayweather took an illegal intravenous injection of saline and vitamins the night before fighting Manny Pacquiao, according to a report from SB Nation.

Much of the delay in Mayweather fighting Pacquiao years earlier, when both were in their primes, was a resistance from Pacquiao to taking Olympic-style drug testing and it led to accusations from Mayweather's camp that Pacquiao was using performance-enhancing drugs.

Larry Merchant Won't Pay Attention To Mayweather Fights Unless He Faces Golovkin

The IV that Mayweather took before fighting Pacquiao did not contain any banned substances, per SB Nation's report, but it can be used as a masking agent. USADA, which conducts drug testing for the Nevada State Athletic Commission, granted Mayweather an exception to take that injection three weeks after the fight occurred, but NSAC director Bob Bennett said that USADA isn't authorized to take that step.

Such an injection is banned because, according to the World Anti-Doping Agency (WADA), it can "dilute or mask the presence of another substance." Further, SB Nation reported that "USADA did not inform the Nevada commission about the IV until May 21," and said that Mayweather received a "retroactive" exemption.

Mayweather's camp justified the injection at the time as a tool to help him re-hydrate following the weigh-in.

Bennett slammed USADA's decision to grant a "therapeutic use exemption" without gaining approval from the NSAC in a report. "The TUE for Mayweather's IV -- and the IV was administered at Floyd's house, not in a medical facility, and wasn't brought to our attention at the time -- was totally unacceptable," Bennett wrote.

"I've made it clear to [USADA CEO] Travis Tygart that this should not happen again. We have the sole authority to grant any and all TUEs in the state of Nevada. USADA is a drug-testing agency. USADA should not be granting waivers and exemptions. Not in this state. We are less than pleased that USADA acted the way it did."

Mayweather's camp did not comment on the matter, and it will not affect Saturday night's fight vs. Berto.

For more content, follow us on Twitter @SportsWN or LIKE US on Facebook