Qualifiers Anastasia Pavlyuchenkova and Anna Kalinskaya pulled off upset wins against seeded opponents in the first round of the Adelaide International on Monday.
In the opening centre court match of the warm-up event for the Australian Open, which runs from January 14-28, 2021 French Open finalist Pavlyuchenkova ousted fifth seed Beatriz Haddad Maia 6-3 6-4.
"I know (she is) a great fighter and (what) if you give her a little bit of a chance to come back," Russian Pavlyuchenkova said of her Brazilian opponent.
"So I knew I had to be 200 per cent against her, and I'm happy it worked," said Pavlyuchenkova, who fired 26 winners compared to Haddad Maia's 13.
Kalinskaya fought for nearly three hours before outplaying fourth seed Barbora Krejcikova 7-5 3-6 7-5.
Krejcikova broke Kalinskaya in the opening game of the third set and raced to a 3-1 lead before the Russian staged a remarkable comeback, cashing in on her third match point to seal victory.
"It was a great match, (Krejcikova is) a very good fighter," Kalinskaya said after her win.
"She plays incredible tennis, she knows how to hit every shot, she made the match very complicated."
Marta Kostyuk won her all-Ukrainian clash with Anhelina Kalinina 7-6(3) 6-1.