The surprises started early at the Australian Open on Day 4, with No. 3 Garbiñe Muguruza becoming the highest-seeded player to exit the women's draw just minutes after No. 6 Anett Kontaveit lost.

Not long after, No. 2-seeded Aryna Sabalenka served a dozen double-faults in the first set and appeared to be on the brink of a second-round defeat before recovering to hold off 100th-ranked Wang Xinyu 1-6, 6-4, 6-2.

Muguruza never managed to earn a single break point and made a whopping 33 unforced errors, more than twice her opponent's total, in a 6-3, 6-3 loss to Alize Cornet under a bright blue and cloudless sky at Rod Laver Arena on Thursday.

"A little bit surprised about my level. I am a little disappointed, too," said Muguruza, who won the season-ending WTA Finals in 2021. "I feel like my shots weren’t as accurate and precise. I feel, also, my aggressive game wasn’t that aggressive today."

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Garbine Muguruza of Spain rests in her chair in a break during her second round match Alize Cornet of France at the Australian Open tennis championships in Melbourne, Australia, Thursday, Jan. 20, 2022.

Garbine Muguruza of Spain rests in her chair in a break during her second round match Alize Cornet of France at the Australian Open tennis championships in Melbourne, Australia, Thursday, Jan. 20, 2022. (AP Photo/Hamish Blair)

Here's how unexpected that result was: Muguruza is a two-time Grand Slam champion and a two-time major runner-up, too, including making it to the final at the Australian Open in 2020.

And the 61st-ranked Cornet? She's appearing in her 63rd career major tournament — and 60th in a row — but never has been beyond the fourth round.

Cornet will get a chance to equal that showing when she plays Saturday, her 32nd birthday.

She called herself "a little bit (of) a dinosaur."

"I don't know how many years I have left," Cornet said. "Today was a perfect gift I could give myself and I really hope the journey’s going to go even farther for me."

Sam Stosur's 6-2, 6-2 loss to No. 10 Anastasia Pavlyuchenkova ended the 2011 U.S. Open champion's 20th, and last, singles campaign at the Australian Open.

"I’ve done more than I ever thought possible. I dreamed of winning a Grand Slam (singles title), and I couldn’t have asked for anything more," Stosur told the crowd in Kia Arena.

Muguruza said she didn't feel at her best physically and noted that the start of this season was "kind of stressful," because COVID-19 spread through her support team and she was apart from them for two weeks.

Kontaveit, who lost to Muguruza in the title match at the WTA Finals, was beaten 6-2, 6-3 by 19-year-old Clara Tauson of Denmark.

"I just went in there believing I could win, but it wasn’t like I have to win," said Tauson, who will make her debut in the third round at a major against 2019 Australian Open semifinalist Danielle Collins. "It was more: ‘I can win, but we’ll see what happens.’"

Sabalenka finished with 19 double-faults, including nine in her first two service games, in her win over Wang. She said she regained her composure during a quick trip to the locker room following the first set.

The U.S. Open and Wimbledon semifinalist from last year said she had "a lot of experience of playing without the serve," and she'd reassured herself that she had enough other weapons to win "even if you can’t serve."

Sabalenka, who entered the year's first major with a chance of reaching the top ranking, has made a stuttering start to 2022, with her service woes including a combined 39 double-faults contributing to first-round losses at tuneup events in Adelaide.

She faces No. 31-seeded Marketa Vondrousova, the 2019 runner-up at Roland Garros, who beat Liudmila Samsonova 6-2, 7-5.

No. 7 Iga Swiatek, the 2020 French Open champion, No. 19 Elise Mertens, Sorana Cirstea and Maddison Inglis, who beat Hailey Baptiste 7-6 (4), 2-6, 6-2, were among the other women advancing. Zhang Shuai of China moved into the third round when No. 12 Elena Rybakina retired from their match while trailing 6-4, 1-0.

On the men's side, fourth-seeded Stefanos Tsitsipas beat Sebastian Baez 7-6 (1), 6-7 (5), 6-3, 6-4 in a second-round match featuring two former junior world No. 1 players.

Other winners among the men included No. 5 Andrey Rublev, No. 15 Roberto Bautista Agut, No. 20 Taylor Fritz, 2014 U.S. Open champion Marin Cilic, No. 32 Alex de Minaur and 70th-ranked Maxime Cressy of the U.S. No. 24 Dan Evans moved on when the player he was supposed to face in the second round, Arthur Rinderknech, pulled out with an injured wrist.

Australian wild-card entry Chris O’Connell upset 13th-seeded Diego Schwartzman 7-6 (6), 6-4, 6-4.

U.S. Open champion Daniil Medvedev, the highest-ranked man in the draw after nine-time Australian Open champion Novak Djokovic was deported for failing to meet the host country's strict COVID-19 vaccination requirements, was playing Nick Kyrgios in a night match.