Sixth-seeded Ons Jabeur and former top-ranked Caroline Wozniacki were eliminated from the Australian Open by two young Russian players in the second round on Wednesday.
Jabeur, the runner-up at Wimbledon last year, made 24 unforced errors as she was beaten 6-0, 6-2 by 16-year-old Mirra Andreeva in 54 minutes.
It is the second successive year that Jabeur has lost in the second round in Melbourne.
Wozniacki, the winner at Melbourne Park in 2018, was beaten 1-6, 6-4, 6-1 by 20-year-old Maria Tomafeeva, who is making her main draw Grand Slam singles debut this year.
Wozniacki, who had two children before returning to the WTA Tour last year after 3 1-2 years away, led by a set and 2-0 before Tomafeeva turned the match around with some devastating hitting, including 40 winners.
Jabeur and Wozniacki played their matches under the roof, on Rod Laver Arena and John Cain Arena, respectively, with rain causing the start of matches on the outside courts to be delayed for several hours.
In the only men's match completed so far Wednesday, fourth-seeded Jannick Sinner beat Jesper de Jong 6-2, 6-2, 6-2 on Margaret Court Arena, the third stadium at Melbourne Park with a retractable roof.
Defending champions Novak Djokovic and Aryna Sabalenka headline the night matches later on Wednesday.
Sabalenka, who won her first Grand Slam singles title here 12 months ago, faces Brenda Fruhvirtova, a 16-year-old Czech player. Novak Djokovic, a 10-time winner of the event, plays local hope Alexei Popyrin.