Ezi Magbegor has placed the Opals on the cusp of Olympic qualification after playing a steady hand in a nervy 60-55 defeat of hosts Brazil.
Australia led by as many as 14 points on Friday morning (AEDT) before a horror offensive stretch saw them go scoreless for almost seven minutes.
Up 49-42 with more than two minutes left in the third period, Sandy Brondello's side scored just six points in the next 11 minutes and trailed by two, to the delight of the rowdy Belem crowd.
But, after restricting a fired-up Brazil to just seven points in the second quarter, they again relied on their defence to seal an important first-up win in the three-game series.
They have Seattle WNBA forward Magbegor (18 points, seven rebounds, four blocks) largely to thank.
The 24-year-old was perfect from the field until missing her final two attempts late in the fourth quarter, while she made two blocks on Brazil's last three shots to shut out the hosts.
"We found a way to win," Magbegor said.
"When offence dries up we have to go to our defence and I think that's what won us the game."
Cayla George blocked the other of those attempts and also hit the decisive triple with one minute to play, while Bec Allen (14 points, seven rebounds, four assists) played with authority.
"Very relieved," Brondello said.
"This is what we come to expect from Ezi; she's still very young but a key at both ends for us.
"Those two stops at the end, that was will and timing and she has this ability to do great things."
Games against Germany and Serbia follow on Sunday and Monday, with only the top three earning passage to the Paris Games from July.
One win could already be enough for the Opals to punch their ticket but victory against Germany, who beat the higher-ranked Serbia earlier on Friday, would assure them safe passage.
Lauren Jackson, chasing her fifth Olympic campaign at 42, played more than eight minutes and came into the game in the first quarter to drill one triple and watch two others rim out.
Brondello has quickly switched focus to the Germans, who are powered by sisters Nyara - who plays for the Opals coach at New York Liberty - and Satou Sabally.
"They're big, bigger than Brazil," she said.
"Satou playing every position on the floor, she's that good.
"We've got our work cut out for us.
"They're dangerous, they handled the occasion well tonight (against Serbia) so we have to be ready and I'm happy we have a day off."
