Floyd Mayweather goes into what he claims will be the last fight of his career this Saturday night under suspicion of doping.

The best pound-for-pound boxer in the world is alleged to have been caught by drugs testers undergoing an intravenous injection at his Las Vegas home the day before his financial blockbuster fight against Manny Pacquiao in May.

The vitamin ingredients of the injection are not of themselves prohibited but most anti-doping agencies ban their use intravenously as this method can be a masking agent for performance enhancing drugs.

Mayweather has never tested positive for drug abuse in his 19-year professional career and his team are claiming that the injection was used to offset dehydration.

Mayweather responded on Thursday with a declaration of his innocence. He said: ‘As already confirmed by USADA, I did not commit any violations of the Nevada or USADA Drugs Testing guidelines.

”I have always followed the rules of Nevada and USADA, the gold standard of drug testing. 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”