Ashleigh Barty described her retirement from Thursday's second-round clash against Magda Linette at the French Open as "heartbreaking".
Top seed Barty required medical attention during her first-round win over Bernarda Pera two days earlier, with a hip injury the cause for concern.
The 25-year-old – back at Roland Garros for the first time since winning her maiden grand slam title in Paris in 2019 – vowed to "play through the pain barrier", yet the injury prevented her from continuing when 1-6 2-2 down against her Polish opponent, who will face Ons Jabeur in the next round.
The Australian's retirement throws the draw wide open, with both of the top seeds now out after Naomi Osaka decided to withdraw amid her disagreement with tournament organisers.
Barty's clay-court season ended with a title in Stuttgart, a runner-up finish in Madrid and an appearance in the quarter-finals in Rome, and she could scarcely hide her disappointment at the way things ended for her in the French capital.
"It's heartbreaking," she told a media conference. "I mean, we have had such a brilliant clay-court season, and to get a little bit unlucky with timing and have something acute happen over the weekend and just kind of run out of time against the clock is disappointing.
"It won't take away the brilliant three months that we have had, as much as it hurts right now.
"We did everything, absolutely everything we could to give myself a chance. It was a small miracle that we were able to get on court for that first round.
"I just tried to give myself a chance and see how it felt. Obviously practicing, we've had our restrictions and essentially tried to stay as fresh as possible and not aggravate it in any way, but in a match that's unavoidable at times.
"It got worse today and it was becoming at the stage where it was unsafe. As hard as it is, it had to be done. Right from the first game, I was battling the pain, and it just became too severe."
SVITOLINA CRUISES THROUGH, PLISKOVA DUMPED OUT
Fifth seed Elina Svitolina booked a third-round meeting with Barbora Krejcikova after seeing off Ann Li 6-0 6-4.
Svitolina landed 74 per cent of her first serves and struck 10 winners to cruise past the American in the opening set.
Li bounced back in the second, roaring into a 4-1 lead, but Svitolina clawed her way back to ensure she reached at least the third round in seven of her nine appearances at Roland Garros.
Svitolina, who overturned a 2-5 deficit in the second set to beat Oceane Babel in the first round, said: "In the end, what I'm really happy with is the way that I was down in both matches in the second set and found a way.
"I found a good level and didn't give up on the second set. That was a really good point for me, and I was really playing composed in both matches. It was two different players, but I was really happy that I could win in two sets in both matches."
Up next is Krejcikova, who overcame Ekaterina Alexandrova 6-2 6-3.
There is no place in the third round for ninth seed Karolina Pliskova, who was soundly beaten 7-5 6-1 by Sloane Stephens, while number 13 seed Jennifer Brady battled past Fiona Ferro 6-1 1-6 6-4.
KENIN WINS BATTLE OF THE AMERICANS
Fourth seed Sofia Kenin defeated fellow American Hailey Baptiste, a qualifier who won four matches in Paris on her French Open debut, 7-5 6-3.
Kenin will now face another compatriot in 28th seed Jessica Pegula, who beat Tereza Martincova 6-3 6-3.
Elsewhere, defending champion Iga Swiatek thumped Rebecca Peterson 6-1 6-1, Coco Gauff got the better of Wang Qiang 6-3 7-6 (7-1), and Elise Mertens edged out Zarina Diyas 6-4 2-6 6-4.