LAS VEGAS • Floyd Mayweather received an intravenous vitamin injection that was banned under World Anti-Doping Agency (Wada) guidelines on the eve of his May fight with Manny Pacquiao, according to a report by SB Nation.
Although the substances contained in the IV were not banned by Wada, IVs are not allowed.
But close to three weeks after the fight, which was won by Mayweather, the American received an exemption from the United States Anti-Doping Agency, the report said on Wednesday.
"It is very disturbing," Bob Arum, Pacquiao's promoter, told USA Today Sports. "Yeah, I am outraged. But I don't know what we can do about it. I can't change the result."
Arum was particularly upset because Pacquiao was denied a pain-killing injection by fight officials for a shoulder injury before the fight, with paperwork discrepancies being cited as the reason.
With the victory, Mayweather remained undefeated at 48-0.
And the 38-year-old is set to face Andre Berto tomorrow in a welterweight world title fight.
The match-up has failed to capture the public imagination.
Mayweather has faced criticism from fans who say he ducked some of the best in the weight division in cherry-picking Berto, who is a massive underdog.
Britain's Amir Khan was among a host of fighters who wanted a go at the pound-for-pound king.
But Mayweather defended his choice of his final opponent.
"Berto is not a pushover. No matter who I choose, the media will have something to say," the world's highest-paid sportsman told a press conference on Wednesday.
He pointed out that Berto had twice been world champion.
"Khan has three losses, Berto has three. No matter what the media say, when it comes down to it, it is two competitors and I know what I can do.
"I can fight. When you talk about highest gates, I am that guy. Highest (television) pay-per-view, I am that guy."
He rejected talk from Virgil Hunter, Berto's respected trainer, that there was some "personal stuff" between the two fighters, who engaged in a seemingly intense face-off after the press conference.
Mayweather also defended what he called his "remarkable" career of 19 years.
"I keep my eyes on the prize and never focus on the outside," he said.