Defending champion Serena Williams has withdrew from the China Open because of a left knee injury.
The 33-year-old power-hitting American has now retired for the second consecutive tournament after pulling out of the Wuhan Open in China last week.
The World number one had been due to face Samantha Stosur in the quarterfinals on Friday, but the Australian will now advance straight through to the semis.
Serena will fly back to Europe to assess the extent of her injury, which puts her participation in doubt for the WTA Finals to be held in Singapore at the end of this month.
The $5.4 million China Open finals will be played on October 5.