Youth edged out experience in the all-Australian clash at Supertubos as Molly Picklum beat Tyler Wright to reach the semi-finals at Rip Curl Pro Portugal.
With World Surf League leader Caitlin Simmers knocked out at the last-eight stage Picklum can move into the lead if she wins at Peniche for the first time.
Strong waves then called off conditions early into the men's last-32 heats on Monday, but not before Jack Robinson had ridden a pair of barrels to score big and make the quarters.
Picklum, 22, picked up two strong scores to defeat two-time world champ Wright, 30, who had been under the weather at the weekend.
Picklum rode seven waves, picking up scores of 6.83 and 6.10 in her fourth and fifth, with Wright's best being her sixth and last, scoring 4.60 to lose on a two-wave tally12.93-7.93.
"I just saw this left, it was dead flat when we first came down, when I saw that I was, 'this is exciting for me'," said Picklum.
"I knew Tyler would stick to her strengths and try and get the rights, so a left running along this sandbank – I am happy I found a few waves and hope that bank stays there."
Gosford's Picklum now faces Florida's Caroline Marks, having won their only previous encounter in the final at Hawaii's Hurley Pro two years ago. Marks won at Superturbos in 2019 while Picklum will be aiming to reach her first final on Portugal's wild Atlantic shore
"You've got to have your eyes up, watch what is unfolding. I feel confident," added Picklum.
In the other semi-final rookie Erin Brooks faces Hawaii's Gabriela Bryan. Brooks, 17, who was born in Texas, moved to Hawaii at nine and represents Canada through her father's birth, edged out Simmers 12.67-12.40.
Only three heats were possible in the men's competition in the third WSL event of the season, and Australians won two of them.
Perth's Robinson picked up waves for 8.17 and 7.50 to thrash Hawaii's Ian Gentil 15.67-2.83 while Brisbane's Liam O'Brien beat American Crosby Colapinto 9.80-8.40.
"It was crazy, this morning was so small, I had my smallest board, then one by one, I went bigger and bigger. I think I took over the locker room," said Robinson, who admitted he "snuck back out" for some more after his heat but called it quits after a fellow rider had their board break.
The pair now face each other guaranteeing Australia a quarter-final place.
Yet to hit the water are two other Aussies. Ethan Ewing, fourth in the WSL standings, faces Frenchman Gatien Delahaye and 21-year-old Sydney rookie Joel Vaughan is up against experienced Moroccan Ramzi Boukhiam.
