Conor McGregor faces sanction if he is disqualified for using MMA tactics against Floyd Mayweather on Saturday. Photo: John Locher, AP

LAS VEGAS – Conor McGregor faces a swingeing fine of millions of dollars if he is disqualified for using any strictly mixed martial arts tactics against Floyd Mayweather.

The richest match in ring history is expected to generate huge purses for the poster boy of the UFC and the best boxer of his generation.

There is a fear that McGregor may use disqualification as an exit from humiliation if he is unable to cope with Mayweather’s wealth of ring experience.

But he stands to lose a substantial tranche of his projected $100 million-plus if he strays outside the Queensberry Rules.

Stephen Espinoza, head of the Showtime Cable whose pay-per-view sales are footing the bill for this extravaganza, said: “It is not in Conor’s interest to do that. It is not the 90 percent penalty which has been mentioned, but it would be a heavy flat fine, an amount very painful to lose.

“It applies only to MMA-style abuses, not to the usual run of boxing fouls like low blows or rabbit punches.”

There is British interest on the undercard, with Nathan Cleverly, the WBA world light-heavyweight champion, defending his regular title against Badou Jack, who is moving up a division following his world super-middleweight title draw with James DeGale in January.

Savannah Marshall, the first UK woman to win a world amateur title, makes her professional debut against American Sydney LeBlanc.