Former champion Caroline Wozniacki advanced to the second round of the Australian Open after four years away as last year's semifinalist Magda Linette retired due to injury while trailing 6-2, 2-0.
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Dane Wozniacki came out of retirement last year after the birth of her two children and reached the fourth round of the US Open where she lost to eventual champion Coco Gauff but showed she could still compete at the highest level.
The 2018 Melbourne Park champion was up 5-2 in the opening set when 20th seed Linette took a medical timeout after struggling to move, and the ailing Pole was unable to continue shortly after going down by two games in the second set.
"It's never nice to see that. Magda is a good friend of mine. I followed her last year and how unbelievably she played last year here," said Wozniacki, who will next play Maria Timofeeva after the Russian beat France's Alize Cornet 6-2 6-4.
"Obviously this isn't how I wanted to finish it. I really hope it's not too serious and she recovers soon."
KREJCIKOVA BATTLES BACK FROM BRINK TO WIN
Former French Open champion Barbora Krejcikova survived a scare to reach the second round beating Japanese wildcard Mai Hontama 2-6, 6-4, 6-3.
The Czech ninth seed, who triumphed at Roland Garros in 2021, struggled with her serve on Margaret Court Arena and was broken six times in total by her 122nd-ranked opponent.
But she dug deep when trailing 3-1 in the second set after losing the opener and eventually turned the tables.
Hontama, 24, playing in just her second Grand Slam, broke twice in the opening set to take a grip on the match.
There were multiple breaks in the second set but Krejcikova produced a powerful forehand winner to hold in the ninth game and edge ahead 5-4, seizing her chance to level the match.
The Czech player, 28, needed a medical timeout when 3-2 up in the decider, receiving heavy strapping to her foot and ankle.
But she showed no signs of discomfort as she returned to the court, conjuring a crucial break in a long eighth game to leave her on the brink of victory, which she sealed when Hontama went long with a forehand.
Krejcikova said she was relieved to get through a "difficult match", which lasted 2hrs 30mins.
"I just tried to stay in the match," she said. "In the second set I was down but I never let go and I never gave up."
ANISIMOVA ENJOYING HERSELF
Amanda Anisimova said she was feeling refreshed and enjoying herself after upsetting 13th-seeded Liudmila Samsonova on her return to Grand Slam tennis following a break to deal with mental health issues.
The 22-year-old American came out on top in her clash 6-3, 6-4, two weeks after returning to action in Auckland following a period of just under eight months away.
"I'm here and feeling good, so we made it," she said, after stepping back from the sport in May, saying it was "unbearable" being at tennis tournaments, citing mental health issues and burnout.
"I'm just here for the journey right now and seeing how much I can progress."
The 2019 Roland Garros semifinalist had to battle back from a break down in both sets against Samsonova, including a 4-1 deficit in the second set.
But she methodically pulled herself back into contention before closing out the match.
"The most important thing is that I feel a lot more refreshed. I'm enjoying practising. I'm enjoying every second that I'm out there," she said.
"Even when I was down today, I was still just enjoying the challenge.
"Yeah, I'm just happy with how I feel coming back. I feel like I was very burnt out while I was playing, and that really wasn't a nice feeling. Being able to just reset is really nice."
Anisimova will next play either Argentina's Nadia Podoroska or Slovakia's Tamara Zidansek.