Australian world number one Ashleigh Barty retired from her Italian Open quarter-final against American teenager Coco Gauff with an arm injury.
Barty, 25, was leading 6-4 2-1 before deciding to stop in damp and cold conditions in Rome.
She ended the match with a compression sleeve on her right arm and also had strapping on her left thigh.
Meanwhile, Wimbledon champion Simona Halep is another leading player who has injury concerns before the French Open.
The Romanian world number three has a "small tear" in her calf after being injured in Rome earlier this week.
The injury casts doubt on the 29-year-old's hopes of playing the French Open - which she won in 2018 - which starts this year on 30 May.
Wimbledon, which was cancelled last year, starts on 28 June.
Halep, who was defending her title in Rome, had to be helped off court after retiring against Germany's Angelique Kerber on Wednesday.
"After an MRI here in Rome I can confirm that I have small tear high up in the left calf," said Halep.
"I will fly home and begin recovery in the pool and gym on Monday. I'm staying positive and will do everything I can to speed up my return."
The exits of Barty and Halep, coupled with earlier defeats for second seed Naomi Osaka, fourth seed Sofia Kenin and 23-time Grand Slam champion Serena Williams, leaves the women's singles wide open.
Gauff, 17, will face either Ukrainian fifth seed Elina Svitolina or French Open champion Iga Swiatek, the 19-year-old from Poland, in the semi-finals.
Former world number one Karolina Pliskova is also through to the last four after saving three match points before beating Latvia's Jelena Ostapenko.
The Czech 2019 champion, who is seeded ninth, won 4-6 7-5 7-6 (7-1) to set up a semi-final against Croatia's Petra Martic.
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