World number one Simona Halep withdrew from the WTA Finals in Singapore with a back injury on Thursday, bringing her season to a premature end.
The French Open champion pulled out of last month's China Open after just 31 minutes, and withdrew from this week's Kremlin Cup because of the persistent problem.
Halep, 27, said she had hoped to compete at the season finale in Singapore, which starts on Sunday, but that she had taken the "tough" decision to put her health first.
"It's always difficult to withdraw from a big tournament," said the Romanian, who sustained the injury in Wuhan last month.
"My back is not okay. I didn't practise for the last four weeks. I'm not ready to compete at this level and I'm still sore."