(Reuters) - World number one Naomi Osaka pulled out of the Italian Open quarter-finals on Friday with a right thumb injury, casting doubts over her participation in this month's French Open.
The 21-year-old Japanese was scheduled to face sixth seed Kiki Bertens after coming through two matches on Thursday in the rain-affected tournament but said she was forced to withdraw due to pain and swelling at the base of her thumb.
"I woke up this morning and couldn't really move my thumb," Osaka told reporters. "I tried to practise and grip my racket but I couldn't, and I kept feeling this pain when I tried to move my hand in different directions.
"Right now I'm... in between sad and disappointed because I really wanted to play my match today. For me, it was sort of a test to play against Kiki because she's playing really well and I wanted to see how well I could do today.
"I didn't feel anything yesterday. That's why I'm kind of confused right now because I literally woke up in the morning and couldn't move my thumb. So I was like, maybe I slept on it and maybe it will go away, but it didn't."
An abdominal injury had forced Osaka to pull out ahead of her semi-final clash in Stuttgart last month before she was beaten by Belinda Bencic in the Madrid Open quarter-finals.
"I would describe (my clay season) as rocky," Osaka added.
"But I can't necessarily say it's been ups and downs because if I think about it, it's definitely been going up. Every match I've played I've learned a lot. I've tried to take what I've learned into the next match and I think I've done that well."
Following her U.S. Open and Australian triumphs, Osaka is chasing a third straight Grand Slam trophy at the French Open which begins on May 26.