World No 1 Iga Swiatek survived a serious examination from German Jule Niemeier in her opening match at the Australian Open in Melbourne.
Niemeier was a surprise quarter-finalist at Wimbledon last summer and also took a set off Swiatek in the fourth round of the US Open.
There was little to choose between the pair on Rod Laver Arena, with Niemeier serving for the second set only for Swiatek to fight back and claim a 6-4 7-5 victory.
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In-form American Jessica Pegula swept into the second round with a 6-0 6-1 win over Jaqueline Cristian in less than an hour on Margaret Court Arena.
The third seed simply overpowered the Romanian in under an hour on court.
"Today's just one of those days, everything's working, I think you just take them as they come throughout the year and I'll just enjoy it," said Pegula.
"It's definitely fun coming in as a top seed, it's a new experience for me."
Pegula, whose parents own the NFL team Buffalo Bills, wrote "Go Bills! #3" with a heart to pay tribute to the NFL team's safety Damar Hamlin, who suffered a cardiac arrest on the field earlier this month.
Compatriot Amanda Anisimova was dumped out in the first round after she lost 6-3 6-4 to 20-year-old Ukrainian Marta Kostyuk.
It was a second straight first-round exit at a Grand Slam for Anisimova, who departed in tears.
Greek sixth seed Maria Sakkari enjoyed a straightforward 6-1 6-4 win over China's Yuan Yue to set up a tie against Russian qualifier Diana Shnaider.
Petra Kvitova, runner-up in 2019, began her campaign by seeing off tricky first-round opponent Alison Van Uytvanck 7-6 (7-3) 6-2.
Victoria Azarenka came through a tough first-round battle against Sofia Kenin 6-4 7-6 (7-3) to ensure she would be the only former Australian Open champion remaining in the women's draw.
"We work hard every day," she said. "The off season is full of blood, sweat and tears so we can go out there and do our best. It's high pressure so I still feel nervous."
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Last year's runner-up Danielle Collins was made to work in her first-round match against Anna Kalinskaya before eventually sealing progress with a 7-5 5-7 6-4 victory, firing 55 winners past the Russian.
Australian wildcard Olivia Gadecki claimed her first Grand Slam match victory when she beat Polina Kudermetova 7-5 6-1 at a raucous Court 8.
Gadecki is being mentored by retired Australian Open champion and former world No 1 Ashleigh Barty.