A hip injury that flared up on the weekend ultimately ended Ash Barty's Roland Garros campaign in the second round.
Barty trailed Poland's Magda Linette 6-1 2-2 before deciding that she could not continue at Court Philippe Chatrier.
"I've had my fair share of tears this week," Barty said.
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"Everything happens for a reason. There will be a silver lining in this eventually. Once I find out what that is, it'll make me feel a little bit better, but it will be there, I'm sure.
"(The injury) got worse today and it was becoming at the stage where it was unsafe. As hard as it is, (the retirement) had to be done."
Magda Linette progresses to the third-round after 2019 Champion Ashleigh Barty retires due to injury, 6-1, 2-2 [ret].
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The world No.1 was the 2019 champion in Paris and had extended her winning streak at the tournament to eight matches with her three-set win over Bernarda Pera in the first round.
But the hip complaint became apparent in that match and it continued to hamper her on Thursday.
An off-court medical timeout did not appear to provide much relief for the Australian, who had been outplayed in the opening set by a tactically astute and consistent Linette.
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Barty struggled for power and upward drive on her serve and her movement lacked its usual speed and freedom; as a result she was forced to go for too much on her shots, or play them out of position, resulting in 18 unforced errors to Linette's nine.
It was a disappointing conclusion to what had been an excellent clay-court season for Barty, who won the Stuttgart title, finished runner-up in Madrid and built a record of 14-3 on the surface before Thursday's retirement.
"It's heartbreaking. It won't take away the brilliant three months that we have had, as much as it hurts right now," Barty said.
"For my body to let me down is really disheartening, but knowing that we also did nothing wrong. It's something that can't be explained at this time.
"It was literally acute, landing on serve one day, and that's all she wrote. It was brutal and tough to accept."
Linette, the world No.45, goes on to play Ons Jabeur, who overcame another Australian, Astra Sharma, 6-2 6-4.