LAS VEGAS — When UFC lightweight champion Conor McGregor signed on the dotted line to face Floyd Mayweather in a boxing match, there was some concern that the mixed martial artist’s instincts would kick in at some point. There was even a clause put into the contract that would fine McGregor if he were to do anything illegal during the fight.

Mayweather would end stopping McGregor in the 10th round in front of over 14,000 fans at the T-Mobile Arena. But the fight did have some dicey moments as McGregor’s muscle memory kicked in and the Irishman would throw some MMA strikes, including hammerfists behind the head.

The individual’s job to ensure this wouldn’t happen was referee Robert Byrd. However, Byrd didn’t appear to be on his A-game tonight as he allowed a lot of things to slide in the fight. McGregor did everything from punching behind the head to some roughhousing, and even some moments where McGregor would get behind Mayweather and throw punches to his body and head. Byrd surprisingly let a lot of these illegal strikes go without warning. And when he did, it was after a prolonged period that could have put Mayweather in danger. This may have been even more surprising considering that Byrd gave an uncharacteristically long speech to both fighters during the face off before the first bell rang and warned McGregor, specifically, about fighting inside of the rules.

But Mayweather would endure and eventually finish McGregor. Afterward, Mayweather addressed Byrd’s job officiating.

“I let the referee do his job. I’m not here to bash the referee. There was a lot of rabbit punching. Things happen, you live and you learn. I just went out there to do my job,” Mayweather said.

When the Nevada State Athletic Commission announced the selection of Robert Byrd, McGregor was pleased because of his belief that he would allow the two fighters duke it out. But not even he could have anticipated him to allow so many things to get by. Nevertheless, it was rare performance by a referee who normally wouldn’t allow such things to slide. Fortunately, nobody was hurt and both fighters put on a performance that excited fans.

More Mayweather-McGregor coverage from Yahoo Sports:
• Mayweather picks up big TKO win over McGregor
• McGregor unhappy with stoppage: ‘Let the man put me down!‘
• Sports world reacts to Mayweather’s 50th career win
• Why was Floyd Mayweather wearing a ski mask?
• Why was T-Mobile Arena so empty for Mayweather-McGregor bout?