Jack Robinson of Australia surfs in Heat 2 of the Opening Round of the Fiji Pro at Cloudbreak, Fiji (AAP Image/Supplied by World Surf League, Aaron Hughes)

Jack Robinson has locked in a spot in the title-deciding World Surf League Finals after winning a heart-stopping round-of-16 clash in the Fiji Pro.

Ranked world No.3 heading into the final stop of the regular season, the West Australian only needed the victory on Friday to secure his berth in the top-five, one-day, winner-take-all showdown at Lower Trestles in California next month.

But the Olympic silver medallist had to scrap his way to a win over Sydney surfer Connor O’Leary, who now competes under the Japan flag.

Robinson trailed O’Leary until the final few minutes at Cloudbreak when his rival blew a golden chance to extend his lead, falling on one of the waves of the heat.

The West Australian then took his own opportunity, scoring a 5.67 for a combined total of 12.34 to topple O’Leary’s total of 11.50.

Robinson will face in-form Brazilian Yago Dora in the quarter-finals.

Queenslander Ethan Ewing was ranked world No.5 heading into Fiji and will take on fellow Newcastle veteran Ryan Callinan later on Friday to keep alive his hopes of a place in the finals.

World No.1 John John Florence was surprisingly eliminated by Hawaiian Imaikalani deVault but already had his California contest date secured.

Second-ranked Griffin Colapinto is also locked in, but will face Gabriela Medina in the quarter-finals at Cloudbreak after both won their round-of-16 match-ups.

The women’s field completed their elimination round early Friday but Australia’s world No.4 Molly Picklum and 10th-ranked Tyler Wright had already moved safely through after heat victories.

Canadian teenage wildcard Erin Brooks upset Hawaiian Gabriela Bryan, pushing her out of the top five, although facing a tough quarter-final contest against world No.1 Caitlin Simmers.

Picklum meets France’s Johanne Defay while Wright faces defending world champion and current No.2 American Caroline Marks.