Australia's former UFC middleweight champion Robert Whittaker has suffered a devastating first-round submission loss to unbeaten Khamzat Chimaev.

Whittaker's prospects of securing another world title shot nosedived in Abu Dhabi on Sunday morning (AEDT), after he tapped out at the 3:34 mark of the opening round.

The 33-year-old Australian landed a couple of leg kicks but didn't have the chance to throw a punch, as he was taken down after just 15 seconds.

He scrambled hard along the cage in an attempt to escape the clutches of the UAE-based Russian fighter, but appeared to suffer an injury to his chin or jaw during the decisive choke move.

"I felt something wrong, a click," Chimaev said.

"Thanks Rob. I love you my brother — you are a legend, I respect you took the fight with me because no-one wants to fight with me."

It was only the second time Whittaker had been submitted and the first time in 13 years.

Renowned wrestler Chimaev, 30, started the fight as favourite despite being ranked 13th, 10 places below the Sydneysider.

They were originally due to fight in June, but Chimaev withdrew after falling ill.

He improved his record to 14-0.

It was only Whittaker's fourth loss in his last 19 fights over a 10-year period, but casts doubt over whether he will ever get another title opportunity.

AAP