Australia's birthday boy Tai Tuivasa has suffered a round-one submission defeat to Marcin Tybura in their heavyweight UFC showdown in Las Vegas.
Tuivasa, who turned 31 on fight night, entered Saturday's bout (Sunday AEDT) ranked ninth in the world and keen to get back on the winners' list following three straight losses.
But he was no match for Poland's world No.9 Tybura, who was left bloodied after copping some early blows but gained the advantage when he tackled Tuivasa to the ground.
Tybura rained a flurry of blows on Tuivasa once the pair hit the canvas, but it was a rear naked chokehold that brought about the Australian's undoing.
Tuivasa fought for breath as he struggled against the chokehold for as long as he could, but the referee stopped the bout with 53 seconds remaining in the first round.
"I feel awesome," Tybura said after the win.
"I got a win over a very strong opponent. Fights like these make me very happy."
The loss is a huge blow to Tuivasa's hopes of climbing his way back up the heavyweight rankings.
Tuivasa's last win in the UFC octagon was in February 2022, when he beat Derrick Lewis in a second-round knockout.
Since then, the man known as 'Bam Bam' has lost to world No.2 Ciryl Gane, world No.3 Sergei Pavlovich, world No.6 Alexander Volkov - and now Tybura.
Fellow Australian Josh Culibao also endured a disappointing result in Las Vegas, losing his featherweight bout by split decision against US fighter Danny Silva.
The judges scored the three-round battle 29-28, 28-29, 29-28.
