World number three Naomi Osaka has withdrawn from the WTA Finals in Shenzhen because of a shoulder injury.
Japan's Osaka, 22, beat Petra Kvitova in three sets in her opening match on Sunday and was due to play world number one Ashleigh Barty on Tuesday.
The Australian Open champion will be replaced in the Red Group by alternate Kiki Bertens, the world number 10.
"I'm disappointed to have to withdraw. This is not how I wanted to end this tournament or my season," said Osaka.
"I look forward to getting healthy and hope to be back here in Shenzhen next year.