Ashleigh Barty and Samantha Stosur have been beaten in straight sets in the second round of the Indian Wells WTA tournament.
Australian world No.21 Barty, who received a bye as one of the top 32 seeds, was upset on Friday by Maria Sakkari of Greece 6-4 6-2.
The 2011 US Open champion Stosur lost 7-5 7-5 to French 14th seed Kristina Mladenovic.
World No.26 Daria Gavrilova, Australia's last hope, will play Yanina Wickmayer on Saturday in the second round.
In a major upset late on Friday, American qualifier Sachia Vickery completed an astonishing comeback to stun third seed Garbine Muguruza 2-6 7-5 6-1 in the second round.
Trailing 3-0 in the second set, Vickery raised her game, brought the Indian Wells centre court crowd alive and eventually wore down an increasingly frustrated Muguruza.
The Spaniard crumpled in the third set as 100th-ranked Vickery clinched the biggest win of her young career.
"She earned this match tonight," Muguruza said. "It was key points here and there.
"I'm going to learn a lot from this match, I'm going to watch it and see what went wrong. It's a little bit sad ... I really love this tournament."
World No.1 Simona Halep began her campaign with a routine 6-4 6-4 defeat of Kristyna Pliskova.
"Today was great in that I could actually play a few rallies," Halep said.
"I got the rhythm back. And I feel good now. I feel more confident.
Sixth-seeded Jelena Ostapenko accounted for Belinca Bencic 6-4 3-6 6-1 while CoCo Vandeweghe overcame Kaia Kanepi 6-0 7-6 (8-6).
Two-time Wimbledon champion Petra Kvitova survived the challenge of Yulia Putintseva to prevail 6-7 (4-7) 7-6 (7-3) 6-4.
Japan's Naomi Osaka earned her second-straight victory over an accomplished star with a 6-3 6-2 defeat of Poland's Agnieszka Radwanska.
The 20-year-old Osaka followed up her straight-sets win over Russian five-time grand-slam champion Maria Sharapova by defeating Radwanska.
The season struggles of British 11th seed Johanna Konta continued with a 7-6 (7-5) 6-4 loss to 18-year-old Marketa Vondrousova.
Aryna Sabalenka and Qiang Wang accounted for seeded players Svetlana Kuznetsova and Elise Mertens, respectively, to reach the third round.
Other second-round victors were Petra Martic and Shuai Zhang.
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