Kristina Mladenovic played through the pain barrier to secure her progress into the second round at Roland Garros on Monday, where she is joined by defending champion Garbine Muguruza.
The French number one was troubled throughout her opener with Jennifer Brady and needed treatment on court before edging a final-set thriller - Mladenovic winning 9-7 in the decider.
Muguruza enjoyed a much easier passage into round two as she came through a potentially tricky clash with 2010 Francesca Schiavone in straight sets.
With Angelique Kerber already out in Paris, Karolina Pliskova could become world number one should she reach the final and Simona Halep fails to win the trophy.
Pliskova beat Zheng Saisai 7-5 6-2 to kick off her quest for the top spot in winning style, the Czech setting up a meeting with world number 86 Ekaterina Alexandrova.
There was no joy for 2015 runner-up Lucie Safarova, though, as she was dumped out by Veronica Cepede Royg, a player ranked 58 places below her.
COURAGEOUS MLADENOVIC FIGHTS ON
Clay has been good for Mladenovic in 2017 with final appearances in Stuttgart and Madrid, and many saw her as France's best hope of a champion given the openness of the women's draw.
An "unlucky" accident on Sunday triggered a bad back and despite medication that continued to trouble her on Court Philippe Chatrier.
The 13th seed managed to block out the pain but expects to be troubled by it in her preparations for a second-round match with Sara Errani - who beat Misaki Doi 7-6 (9-7) 6-1.
"My back feels so-so," she told a media conference. "[An] unlucky thing happened to me yesterday and I locked my back. I had a spasm.
"This morning it was better, but it was really bad for being at the top level of playing and especially on the serve.
"I just dug in, I really don't know how I managed that."
MUGURUZA EYES STUTTGART REVENGE
Muguruza's form has been far from ideal heading into her first grand slam title defence but she will get the chance for revenge in round two.
The Spaniard has lost three of her seven matches on clay in 2017 and one of those defeats came against Anett Kontaveit in Stuttgart.
After victories on Monday the pair will meet again in round two, and Muguruza hopes for a different outcome this time around.
"I heard I was playing with her again. It's another tough match for the second round," she said.
"I played her in Stuttgart and she played very well there. I saw her also in Rome. She did well, [playing] Kontaveit in second round I think is difficult."
END OF THE LINE FOR SAFAROVA AND JANKOVIC
Not everyone can be winners and two former semi-finalists bowed out as Jelena Jankovic and Safarova were beaten.
Jankovic lost 6-2 7-5 to Richel Hogenkamp early on, while Safarova made 25 errors in her defeat to Cepede Royg.
There was disappointment for Lauren Davis too, the 25th seed allowing Carina Witthoeft to come from a set down and seal a place in the next round.
Davis was not the only seed to bow out as Daria Gavrilova and Coco Vandeweghe were also surprise casualties.
Caroline Wozniacki battled back to ensure she did not suffer the same fate at the hands of 17-year-old world number 337 Jaimee Fourlis, while former US Open champion Sam Stosur is also safely through.
NUMBER ONE IN SIGHT FOR PLISKOVA
Pliskova has moved up the WTA rankings in 2017 and her consistency will be rewarded with top spot should she maintain the performance that saw her beat Zheng 7-5 6-2.
Halep could still spoil her ascension but Pliskova is solely focused on improving on her previous best in Paris by reaching the third round.
"There are always some nerves and some kind of pressure, especially on grand slams it's a little bit harder than the normal tournaments," she said.
"I think it is usual that everyone is nervous, not only seeded players and not only the ones who have pretty high expectations. But once I'm on the court it's fine."