The underdog could only mutter that it "feels good" to beat Mairis Briedis and claim his IBF and The Ring cruiserweight world title belts after a brutal 12 rounds at the Gold Coast Convention and Exhibition Centre on Saturday night.

Opetaia has always let his actions do the talking.

An Olympian at 16, he is now world champion at 27 after a unanimous points decision that marked just the second loss of the stoic Briedis's 30-fight professional career.

It was revealed by doctors in an emotional dressing room that his jaw had been fractured on both sides of his mouth, first on one side in the second round and then again on the other side in the sixth round.

Opetaia went straight from the stadium to the emergency department, had surgery on Sunday night and faces at least three months out of the ring.

He said "he felt it crack" after a Briedis uppercut, promoter Dean Lonergan labelling it one of "the most brutal fights in Australian boxing history".

"One of the all time great performances, not only of Australian boxing, but Australian sport and we should be celebrating him for a long time," he said.

"That was just stunning and he should be celebrated as an Australian hero and I hope he gets the accolades he deserves.

"All you do (to promote his next fight) is put it on. He showed everything."

Opetaia is already fielding offers, greeted by a challenge from current WBO champion Lawrence Okolie, who holds the belt Opetaia had promised his late grandfather he'd win.

"He's gotta enjoy the belts but OMG, what a fight (that) has just been set up. Imma show Briedis how it's f***ing done," he tweeted.

Briedis marched straight out of the ring after the decision - judges awarded Opetaia the fight 116-112, 115-113, 116-112 - later congratulating him in the dressing room and asking for a rematch.

He was surprised to hear Opetaia had suffered a broken jaw so early in the fight, before revealing his nose was broken, "so that makes it one-all".

"Did you enjoy this fight?," he asked media, accepting of the officials' decision.

"Enjoy your world champion."

Opetaia had already been dubbed the toughest Australian boxer by Jeff Fenech, given he was lucky to even be in the ring after a freak rib injury in April delayed the bout and left doctors scratching their heads.

Dr Andrie Stroebel told AAP that he'd never seen anything like it, the surgeon using "3D rib clips" to attach torn cartilage back to the bone before it was pummelled by Briedis.

Only current heavyweight world champion Oleksander Usyk had beaten the 37-year-old Latvian, who surged back into the fight in the final five rounds after Opetaia had started well to bloody his nose and close his left eye.

Several big blows rocked Opetaia in the 10th round but he steadied and the pair stood and traded blows in an epic final round, as only then the damage to Opetaia's jaw became visible.

Earlier in the night, Issac Hardman produced a sickening first-round knockout of Beau Hartas.

Responding to a comprehensive loss to Michael Zerafa, Hardman's thunderous right hand floored Hartas.

It left him motionless on the canvas for more than a minute before he stirred and exited the ring on his feet.

Australian Associated Press