Australia assured their place in the quarter-finals of the women's beach volleyball when their two teams met in the last 16 knockout stage on Friday.
Natalie Cook and Nicole Sanderson triumphed 21-15 21-16 over Kerri Pottharst and Summer Lochowicz.
Cook and Pottharst were partners when they won gold at the 2000 Games.
Elsewhere, Italy beat Germany 16-21 21-17 21-19 while Brazil maintained their quest for a medal with a 21-16 21-19 win over home favourites Greece.
Italian pair Daniela Gattelli and Lucilla Perrotta will play Cook and Sanderson for a place in the last four on Sunday.
Cook said she laughed when she found out she would be facing her former partner.
"With Kerri knowing my game inside and out it was kind of a mental headache to know what to do," she said.
In the men's competition, United States duo Daxton Holdren and Stein Metzger caused an upset when they beat Germany's Markus Dieckmann and Jonas Reckermann 21-16 19-21 15-13.
The Americans will now face Switzerland in the quarter-finals after Patrick Heuscher and Stefan Kobel beat Portugal's Joao Brenha and Luis Miguel Maia 21-18 21-19.