Floyd Mayweather may have won in the ring on Saturday, but he may face another battle - in court. 

Ex-girlfriend Josie Harris filed a lawsuit on Tuesday against the champion boxer for $20 million for defamation after Mayweather claimed Harris was on drugs during a 2010 domestic violence incident, reports CNN

Mayweather claimed in an interview with Katie Couric that instead of beating Harris, he was simply restraining her because she was on drugs. He was arrested in September 2010 after he punched Harris at his home in Las Vegas. 

The boxer pleaded guilty 14 months later to misdemeanor battery and two counts of harassment. The judge sentenced him to three months in prison; he served two out of the three months. 

But Mayweather is tracking back. During his interview with Couric, he said. "Did I kick, stomp, and beat someone? No, that didn't happen. ... Did I restrain a woman that was on drugs? Yes, I did. So if they say that's domestic violence, then, you know what? I'm guilty. I'm guilty of restraining someone."

He also dodged Rachel Nichols' questions about his domestic violence incidents, saying it was all "just hearsay and allegations." Harris said she is not a drug abuser or addict and her attorney said, "It was not Mayweather's 'restraint' of Harris that caused serious injuries, rather it was his beating of her," reports CNN.

The lawsuit also states that after the incident, she had to receive treatment for head, facial and bodily injuries. 

Saturday's fight against Manny Pacquiao was the most lucrative fight of Mayweather's career. He has already been paid $100 million and stands to earn another $100 million, according to sports media experts.