Two former Grand Slam champions shook up the women's singles field at the Australian Open on Sunday.

Reigning Wimbledon champion Elena Rybakina took down top seed Iga Swiatek in straight sets, while 2017 French Open winner Jelena Ostapenko knocked out Coco Gauff.

Swiatek's loss to Rybakina was just the third loss suffered by the top-seeded Pole in the last five Grand Slams.

Rybakina has now taken out two of the four semifinalists from last year's Australian Open. She defeated Danielle Collins in the third round.

Ostapenko earned her first quarterfinal appearance in a Grand Slam since Wimbledon in 2018 with her upset over the American teenager Gauff.

The upsets could be welcome news for American Jessica Pegula, who won her fourth consecutive match in two sets over former French Open champion Barbora Krejcikova.

The upsets extended to the men's singles bracket as well, as No. 6 seed Felix Auger-Aliassime and No. 10 seed Hubert Hurkacz fell on Sunday.

Hurkacz lost to rising American star Sebastian Korda, who will face Karen Khachanov in his first-ever Grand Slam quarterfinal match.

Auger-Aliassime's and Hurkacz's exits made Stefanos Tsitispas the clear favorite to reach the men's final from the top half of the bracket. Tsitsipas won the match of the day in five sets over Jannik Sinner.

Sunday Results

Men's Singles

No. 3 Stefanos Tsitsipas def. No. 15 Jannik Sinner, 6-4, 6-4, 3-6, 4-6, 6-3

Jiri Lehecka def. No. 6 Felix Auger-Aliassime, 4-6, 6-3, 7-6 (2), 7-6 (3)

No. 29 Sebastian Korda def. No. 10 Hubert Hurkacz, 3-6, 6-3, 6-2, 1-6, 7-6 (7)

No. 18 Karen Khachanov def. No. 31 Yoshihito Nishioka, 6-0, 6-0, 7-6 (4)

Women's Singles

No. 22 Elena Rybakina def. No. 1 Iga Swiatek, 6-4, 6-4

No. 3 Jessica Pegula def. No. 20 Barbora Krejcikova, 7-5, 6-2

No. 17 Jelena Ostapenko def. No. 7 Coco Gauff, 7-5, 6-3

No. 24 Victoria Azarenka def. Zhu Lin, 4-6, 6-1, 6-4

Elena Rybakina Knocks Out Iga Swiatek

Rybakina authored one of the best performances against Swiatek since the Pole established herself as one of the best women's singles players in the world.

The Kazakhstani took care of Swiatek in straight sets to reach the third Grand Slam singles quarterfinal of her career. The 22nd seed won Wimbledon last summer and made it to the final eight at the 2020 French Open.

Rybakina broke Swiatek's serve on four occasions, produced four more aces than the top seed and delivered nine more winners over the 89-minute match.

All three of Swiatek's losses at a Slam since 2022 have come in straight sets. She fell to Alize Cornet in the third round at Wimbledon last year and dropped a semifinal clash with Collins a year ago in Melbourne.

The 23-year-old's upset over Swiatek made some Grand Slam history. The 2023 Australian Open marks the first time in the Open era in which the top two seeds in the men's and women's singles draws were eliminated before the quarterfinals, per ITF Media.

Rybakina is a real threat to win the title, but the top half of the women's bracket will be tough to navigate.

Her next opponent, Ostapenko, is in the best form she has been in in quite some time. The 25-year-old won the 2017 French Open and reached two other quarterfinals. That experience should help her against Rybakina.

Pegula is the top seed left in the top half of the bracket. The third-seeded woman is also the only American woman left in the competition.

The Buffalo, New York, native could be viewed as the favorite to win the tournament going into the final eight.

The 28-year-old has not gotten past the quarterfinal stage at a Grand Slam, but what she lacks in experience, she makes up for in her current form—the best of any player in Australia.

Pegula faces a challenge in the quarterfinals against Victoria Azarenka, a two-time Aussie Open champion who is looking to make her first semifinal Slam appearance since the 2020 U.S. Open.

Sebastian Korda Makes First Grand Slam Quarterfinal

Sebastian Korda continued the fantastic tournament for American men by securing his first-ever Grand Slam quarterfinal berth.

The 29th seed battled over five sets with Hubert Hurkacz and captured a thrilling fifth-set tiebreak.

Korda is aiming to become the first American man to win a Grand Slam singles title since Andy Roddick won the 2003 U.S. Open.

The bracket has opened up for an unlikely finalist to emerge from the top part of the bracket. Tsitsipas is the only top-16 seed left in that part of the draw.

Korda already eliminated No. 7 seed Daniil Medvedev in the third round, so he should go into a potential semifinal with Tsitsipas with plenty of confidence that he can win and land a potential meeting with Novak Djokovic.

At least two American men will be in the final eight. Ben Shelton and J.J. Wolf play each other in the fourth round Monday, and Tommy Paul faces Roberto Batista Agut. Shelton, Wolf and Paul all reside in Djokovic's half of the bracket.

Tsitsipas should be viewed as the favorite to face Djokovic in the final because he is the best player left in the top half.

The third-seeded Greek has been to three Australian Open semifinals in the last four years. He should be well rested for a semifinal match against Korda or Karen Khachanov since he faces unseeded player Jiri Lehecka in the quarterfinals.

The Pole likely did Tsitsipas a favor by beating Auger-Aliassime on Sunday. The Canadian was the only other top-10 seed left in that part of the draw after Hurkacz's loss.

Tsitsipas may be too much for Korda to handle if the two players meet in the semifinals, but with the way the tournament is going, the unlikely result has the potential to happen.