Ashleigh Barty needed a medical time out at the end of the second set against Bernarda Pera
World number one Ashleigh Barty came through an injury scare to avoid a shock in the French Open first round against American Bernarda Pera.
Barty, whose solitary Grand Slam title came in Paris in 2019, took the first set but needed lengthy treatment on her left hip after losing the second.
However, the Australian recovered to beat world number 70 Pera 6-4 3-6 6-2.
Elsewhere, fifth seed Elina Svitolina survived a second-set fright to beat teenage debutant Oceane Babel 6-2 7-5.
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With second seed Naomi Osaka withdrawing from the tournament after the controversy over her refusal to speak to the post-match media, Barty is guaranteed to remain top of the world rankings regardless of results at Roland Garros.
She will face Magda Linette in the second round after the Polish player defeated France's Chloe Paquet 6-3 6-3.
Seven-time Grand Slam champion Venus Williams, 40, suffered a fourth consecutive French Open first-round exit as she was beaten 6-3 6-1 by Russian 32nd seed Ekaterina Alexandrova.
But American teenager Coco Gauff, the 24th seed, came through a marathon first set to eventually see off Serb Aleksandra Krunic 7-6 (13-11) 6-4 in two hours and seven minutes.
Gauff, 17, won an 83-minute opening set on her way to setting up a second-round meeting with China's Wang Qiang.
Barty truly tested on Roland Garros return
Top seed Barty was playing her first match at Roland Garros since beating Marketa Vondrousova in the final two years ago, having opted not to defend her title in 2020 because of concerns over travelling during the Covid-19 pandemic.
She was pushed harder than many expected by Pera, who broke Barty twice in the opening set, only to surrender her own serve three times in her return to Court Philippe Chatrier.
Barty looked out of sorts in the second set as Pera, whose only win over a top-10 player came against Britain's Johanna Konta at the 2018 Australian Open, grew in confidence with a string of impressive winners.
However, the 25-year-old top seed regained her composure and movement in the decider, helped by a number of unforced errors from an increasingly-erratic opponent whose earlier accuracy deserted her.
If she is to reclaim the title she won two years ago, it appears Barty will have to do so through the pain barrier, now battling a hip issue that comes after a right arm injury that forced her withdrawal from last month's Italian Open.
"It's going to be a little bit tough this week," said Barty, who had not progressed beyond the second round in Paris in five attempts before her 2019 triumph.
"I'm not going to hide behind the fact I'm not quite 100% but I can guarantee that I will go out there with the right attitude every day and be really accepting of that and give it a crack no matter what."
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Svitolina given fright by teen debutant Babel
Elina Svitolina has reached the quarter-finals three times at Roland Garros but is yet to progress further
Earlier on Court Philippe Chatrier, world number six Svitolina fought back from a break down in the second set to bring 17-year-old Paris native Babel's first senior Grand Slam appearance to an early end.
After losing a one-sided opening set, Babel threatened a fightback as she led 5-2 in the second but Svitolina won five successive games to progress.
Svitolina will meet Ann Li in round two after the American thrashed Russia's Margarita Gasparyan 6-0 6-1.
The Ukrainian was made to work hard for her victory by Babel, who was playing an opponent ranked inside the world's top 150 for the first time.
"It's a first time for her to play here in the main draw of the Grand Slam and to face the sixth player in the world it's extremely tough," Svitolina said.
"I think she dealt very well with it and she went for her shots in the second set and made life very difficult for me."
Australian Open finalist Jennifer Brady beat Anastasija Sevastova 6-3 6-3, while Greek 17th seed Maria Sakkari defeated Ukraine's Katarina Zavatska 6-4 6-1.
Czech ninth seed Karolina Pliskova also progressed, seeing off Croatia's Donna Vekic 7-5 6-4 on Court Suzanne Lenglen.
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