Wimbledon champion Marketa Vondrousova crashed out of the Australian Open at the first hurdle on Monday, succumbing to Ukrainian qualifier Dayana Yastremska 6-1, 6-2.
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The Czech seventh seed pulled out of the warm-up Adelaide International last week with a hip injury and her court movement appeared to be impaired in Melbourne.
She lost her opening service game and never got back in the contest as 93rd-ranked Yastremska took control on John Cain Arena, surging through the first set in just 31 minutes.
Vondrousova, who beat Australian Open sixth seed Ons Jabeur for her breakthrough at the All England Club in July, was broken again at the start of the second set and there was no way back.
"Today was a really nice game," said Yastremska, who hit 26 winners to Vondrousova's five.
"I was a little bit nervous, but I just tried to enjoy myself. Today, I felt huge support from the crowd."
It was her fourth career win over a top-10 player, most recently beating then world No 3 Barbora Krejcikova in Dubai in 2022.
Yastremska, whose best showing at Melbourne Park is a third-round appearance in 2019, will next play France's Varvara Gracheva, who is unseeded.
GAUFF FINDS RHYTHM TO REACH SECOND ROUND
Coco Gauff eased into the second round, beating unseeded Anna Karolina Schmiedlova 6-3, 6-0 in a one-sided affair on centre court.
The American, bidding to become the first woman since Naomi Osaka in 2018-19 to win the US Open and Australian Open back-to-back, made a nervy start.
But she still had too much for her struggling Slovakian opponent, who failed to win any of her seven service games.
Fourth seed Gauff broke Schmiedlova, ranked 68, four times in the opening set with two holds proving decisive for the 19-year-old, who defended her Auckland title earlier this month.
She found more of a rhythm in the second set, taking it 6-0 in just 25 minutes on a sun-baked Rod Laver Arena.
"I was a little nervous in the first set and I think I did well returning and then I found my serve towards the end (of the set)," she said.
The teenager said she was always nervous in the first round of a major, adding that she had to give herself a talking to on court.
She said she told herself: "'I feel good, I look good so just have fun.' I was able to relax."
Gauff will play unseeded American Caroline Dolehide in the second round.
SIXTH SEED JABEUR CRUISES INTO SECOND ROUND
Ons Jabeur swept into the second round with a comprehensive 6-3, 6-1 victory against Ukrainian qualifier Yuliia Starodubtseva on Monday.
The Tunisian sixth seed, a three-time Grand Slam runner-up, was not at her best but had too much firepower for her 23-year-old opponent, who was making her debut in the majors.
Jabeur, beaten in the second round in Melbourne last year, said she was nervous in her first match of the year, having opted not to play warm-up tournaments.
"It's very, very special to come back here," she said. "I decided to rest a bit before coming to the Australian Open.
"The crowd helped today and hopefully it will be a much better match for the next round."
Jabeur hit 28 unforced errors and 15 winners during the match on Margaret Court Arena but crucially broke serve six times.
The 29-year-old lost her opening service game against 150th-ranked Starodubtseva when she double-faulted but engineered three breaks of her own to take the first set.
Her serve was rock-solid in a one-sided second set lasting 30 minutes, in which she conjured three more breaks.