Mayweather vs. McGregor—is it really on?

Floyd Mayweather Jr. throws a right at Andre Berto during their WBC/WBA welterweight title fight at MGM Grand Garden Arena on September 12, 2015 in Las Vegas, Nevada.
Ethan Miller | Getty Images

The sporting world was awash with rumors over the weekend contemplating the prospect of a fight between Floyd Mayweather and Conor McGregor.

Undefeated boxer Mayweather has admitted that he started the talk of a return to the ring against a mixed martial arts fighter - thought to be UFC's Conor McGregor.

In a response Sunday, McGregor tweeted a mock-up picture of himself squaring off against the five-weight world boxing champion.

Conor Tweet

"Keep your fingers crossed, it may be a boxer versus an MMA fighter," Mayweather – now retired - told industry website

"It was a name that was shot at me. It may not be a rumor."

Meanwhile, McGregor has told British media that he wants a "billion-dollar fight" against the American, while Mayweather has said he would want to be paid $100 million to fight the 27-year-old Irishman.

After Mayweather's last fight in September he claimed his professional boxing career, with an unblemished 49 wins, was over.

McGregor was pulled from a UFC event in April after refusing to fulfill promotional duties.