The "Battle of the Sexes," a 1973 tennis match between Billie Jean King and a former Grand Slam champion, was rigged by the mob, according to a new report.

The tennis match between King and the late Bobby Riggs, a former Wimbledon and U.S. Open champ, was a spectacle watched by millions around the world Sept. 20, 1973. More than 30,000 people packed the Houston Astrodome to see whether King, 29 at the time, could defeat a man.

King beat Riggs, who was 55 at the time of the match, 6-4, 6-3, 6-3. The win gave women's tennis a huge boost in terms of respect and gender equality, but an ESPN "Outside the Lines" report says the whole match was fixed because Riggs owed mobsters more than $100,000 and threw the match to erase the debt.

Hal Shaw, who was an assistant golf pro at a Florida country club, says he overheard two infamous mobsters discussing Riggs months before the legendary match.

"They brought up the name of Bobby Riggs, and Riggs assured him that he would go in the tank, and he'll make it look and appear that he's trying his best but Billie Jean King was just overwhelming him," Shaw told "Outside the Lines."

ESPN's Don Van Natta interviewed Shaw for the piece, which aired Sunday.

"I looked in his eyes, I heard him tell the story multiple times, the details were always the same," Van Natta said. "I was not going to move forward with this story unless I believed him to be someone who was absolutely credible."

In an interview with ESPN, King disputes Shaw's account.

"I would bet my life that Bobby never had that discussion with them," she said. "Bobby doesn't get involved in mobsters."

King also released a statement calling the entire story "ridiculous."

"I was on the court with Bobby and I know he was not tanking the match. I could see in his eyes and body language he wanted to win," she said.

"It was 40 years ago and I won the match and I am 100 percent sure Bobby wanted to win as badly as I did. Those who bet against me lost money but the result is the same today as it was 40 years ago."

Riggs died in 1995 at the age of 77, but his son says his father knew people within the mob.

"Did he know mafia guys? Absolutely," Larry Riggs said. "Is it possible they talked to him about doing it? Possible."