UFC president Dana White was left grimacing at the sight of one of Power Slap’s most brutal KO’s in the sports’ short history.

White was sat in the front row as Jay Rivera was knocked unconscious by Joshua Boisvert during the first bout of the ‘Power Slap: Road to the Title’ reality television series.

RumbleRivera was knocked out cold in the opening bout of Power Slap: Road to the Title[/caption]

The programme follows a format similar to the UFC‘s popular ‘Ultimate Fighter’ show, where competitors are split into two teams and placed in a house together before squaring off in the arena.

‘Road to the Title’ is now in its third season and in the first bout of the series, Rivera and Boisvert exchanged blows in the lightweight tournament.

Rivera won the coin toss and so took the first slap.

Boisvert flinched, allowing Rivera to take a re-slap, although he wasn’t able to floor his foe on either attempt.

When it was eventually Boisvert’s turn to step up, he caught Rivera hard and switched his lights off.

Rivera banged his head on the table on the way down and was left sprawled out on the canvas.

He lay there for a few seconds unresponsive while the camera switched to White, who looked visibly concerned.

“He’s still hurt,” said White, grimacing.

Rivera eventually made his way onto a stool but it took him a considerable stretch of time to get his senses back.

While Rivera insisted he would be back, his coach Austin Turpin urged him to retire in the immediate aftermath.

RumbleRivera banged his head on the table on the way down[/caption]

RumbleRivera was slapped flat on his back[/caption]

RumbleWhite was visibly concerned for the fallen fighter[/caption]

“Jay has got an issue with his chin,” said Turpin.

“He might love this sport, he might want to do it. But he might be better off as a fan.”

Rivera added: “My opponent, he got a pretty good shot in. First hit was a flinch foul, hit my thumb.

“Tried to take it again but I couldn’t take him down. He got me good.

“I love this sport, it’s such a great event. I would definitely love to come back and keep doing this more.”