Mixed martial arts: Kiwi Brad Riddell suffers knockout loss at UFC Fight Night in tense fight with Rafael Fiziev

Kiwi Brad Riddell is no longer undefeated in the UFC after suffering the first knockout loss of his career on Sunday in Las Vegas.

Matched up against former training partner Rafael Fiziev, Riddell went blow for blow with the Kazak in a tense first two rounds, before a spinning wheel kick from Fiziev swiftly ended the bout midway through the final frame.

The result snaps a seven-fight win streak for the City Kickboxing lightweight and could see Riddell drop out of the top 15 rankings.

It's a blow for Riddell's rise through the division after working his way to No.12 with four impressive victories since making his Octagon debut in 2019.

The pair of technical strikers remained friends following their stint at Tiger Muay Thai in Thailand several years ago, where Riddell was the famed gym's striking coach.

A humble Fiziev said post-fight he hopes the Christchurch-native bounces back from defeat.

"I love him," Fiziev said in his post-fight interview. "When I meet him I love him from the first second, he's a very good guy.

"I learned from him before and today, also. I hope he will come back."

Riddell started the UFC Fight Night co-main event well, controlling the first round with distance, although Fiziev landed several heavy body kicks and a stinging counter right hook, while the second was just as close with the Kiwi suffering a cut above his left eye thanks to a slicing elbow.

Riddell scored a final round takedown in hopes of securing victory but he couldn't keep Fiziev down and with just a touch under two minutes remaining in the fight, he was left dazed following the stunning kick and referee Herb Dean stopped the contest.

"I waited for this moment, three rounds," Fiziev said.

"I did not turn because I know when he goes this way, he drops his hands down and he forgets about spinning back kicks."