Controversy reigned at the first UFC event of 2025 as the bout between Roman Kopylov and Chris Curtis produced an action-packed battle, and a hotly-disputed last-second stoppage.

The middleweight bout between Curtis and Kopylov at UFC Vegas 101 was already set to be one of the highlights of the evening as the bout headed into its final seconds, but the last-gasp intervention of referee Mark Smith led to a buzzer-beating TKO victory for Kopylov, and an angry reaction from Curtis.

More news: Kickboxing Ace Cesar Almeida Delivers Jaw-Dropping Come-From-Behind Knockout at UFC Vegas 101

Kopylov and Curtis had traded big punches back and forth over the course of a fight that left both men battered and bruised as the action moved into the closing stages of the fight.

With the fight hanging in the balance heading into the final round, both men left it all in the Octagon as they swung for the fences in search of a last-round finish.

Kopylov stung Curtis with some big left hands that put the American on unsteady legs, but Curtis fired back with shots of his own as he wore down the increasingly exhausted Russian.

Then, after the 10-second clapper sounded, both men stood toe to toe and exchanged for one final time, and a surprise head kick from Kopylov rocked Curtis, who stumbled and fell to the canvas.

Rather than move in and land more shots to the grounded American, Kopylov mercifully stepped away, but referee Smith decided he had seen enough, and waved off the action with just one second left on the clock.

More news: Former UFC and WWE Champion Ronda Rousey Welcomes Birth of Second Child

It meant Kopylov earned a dramatic last-second TKO victory as Curtis vociferously protested the stoppage. Unfortunately for Curtis, the decision had been made.

Had Smith allowed one more second to elapse, the fight would have gone the distance and the judges would have been called into action. The official scorecards showed that all three judges had scored the fight level at one round apiece heading into the final frame.

The defeat was a bitter pill to swallow for 37-year-old Curtis, who had battled back from a nine-month injury layoff to face Kopylov at the UFC APEX in Las Vegas, and he was left to head back to the locker room after suffering only the second KO/TKO defeat of his 44-fight career.

Kopylov, meanwhile, celebrated the 14th win of his career, and his sixth in the UFC, as he claimed a dramatic victory to get his year off to a flying start.

For more on MMA, head to Newsweek Sports.