Naomi Osaka's season appears to be over after she said she will not play at next month's Billie Jean King Cup Finals because of injury.
The four-time Grand Slam singles champion said in Tokyo on Sunday that she had ruptured abdominal muscles.
"I thought I strained my back, but I did an MRI in Beijing and they said that I bulged a disc in my back and I also ruptured abdominal muscles," Japan's Kyodo News agency reported the 27-year-old as saying.
Osaka has been sidelined since she retired from her last-16 match at the China Open against eventual champion Coco Gauff at the start of the month.
She pulled out of the Japan Open in Osaka and this week's Pan Pacific Open in Tokyo. On Monday, organisers of the Hong Kong Tennis Open announced that Osaka's season was over and that she would not participate in the tournament, which starts October 28.
"Naomi Osaka has been forced to withdraw from competing at the Prudential Hong Kong Tennis Open 2024 due to injury, in an unfortunate end to her tennis season in 2024," said a statement on social media.
The Billie Jean King Cup Finals would have been the last event on Osaka's 2024 schedule.
"I've played so many tournaments this year, so it was definitely the toughest decision to not play this and obviously not play BJK," she said.
"I really honestly enjoyed it so much, and I think it helped with my development as a player."
The Billie Jean King Cup Finals take place in Malaga, Spain, on November 13-20.
Osaka helped Japan beat Kazakhstan in April to qualify for the finals in her first Billie Jean King Cup appearance since 2020.
Her appearance at the China Open was her first tournament under Patrick Mouratoglou, the Frenchman best known for being the long-time former coach of Serena Williams.
She has struggled for consistency since returning to tennis in January after the birth of her daughter Shai in July 2023.
Her best results since becoming a parent have been two quarter-final appearances.