You could write 1,000 predictions for this year's Rugby League World Cup, and Keaon Koloamatangi starting at hooker for the Mate Ma'a Tongan outfit still wouldn't have cracked the list.

The South Sydney back-rower, originally named in his natural position out wide - made the late switch into dummy-half after Siliva Havili was ruled out of the contest - starring in the role.

Havili picked up a calf injury in the Rabbitohs' semi-final victory over the Cronulla Sharks, missing their preliminary final loss to the Penrith Panthers as well as the early stages of the tournament.

AUCKLAND, NEW ZEALAND - NOVEMBER 24: Siliva Havili reacts during the Tonga Rugby League World Cup Semi Final Captain's Run at Mt Smart Stadium on November 24, 2017 in Auckland, New Zealand. (Photo by Hannah Peters/Getty Images)

Koloamatangi made the late switch an hour before kick-off with limited hookers in the side, young Warriors' hooker Taniela Otukolo the only other recognised No. 9 in the Tongan squad.

Despite playing an unfamiliar position, Koloamatangi still managed nearly 150 metres, 34 tackles as well as scoring the match-winning try, his first for Tonga.

With Havili still considered a 50/50 chance of recovering from his calf injury to face Wales this weekend, head coach Kristian Woolf refused to rule out continuing the experiment throughout the tournament.

"We'll figure out whether we persist with it through the week," Woolf told AAP.

"We just wanted to put someone in there who had the skill.

"He did a great job I thought, some of his passes weren't right on point but he can defend there, keep it simple and he got us off to the right start."

While a cloud surrounds Havili still, the picture is slightly clearer for the return of Will Hopoate, who is aiming to make his comeback in the final pool game.

"He (Hopoate) won't play next week but he's a real chance against the Cook Islands," Woolf added.

"I know what sort of class Will's got and with St Helens we never lost a game with him this year.

"That speaks volumes of his class and his influence on this team and I know how much it means to him to play for Tonga."

Tonga will face off against Wales in the early hours of Tuesday, kicking off their second pool game at 5:30 AEDT.