Naomi Osaka has withdrawn from the WTA Finals in Shenzhen after one match due to a shoulder injury, the world No 3 announced on Tuesday.
Osaka, the reigning Australian Open champion, made a winning start to her tournament at the season-ending event in China, defeating Petra Kvitova on Sunday.
However, hours before her second group stage match against top-ranked Ashleigh Barty, Osaka pulled out of the tournament.
“I’m disappointed to have to withdraw from the Finals," the 21-year-old Japanese player said. "This is not how I wanted to end this tournament or my season. I look forward to getting healthy and hope to be back here in Shenzhen next year.”
Osaka has experienced a mixed season on the WTA Tour, starting with the high of winning a second grand slam title when she won in Melbourne to follow her US Open triumph in September last year.
That victory in Australia propelled her to world No 1 for the first time in her career - a status that appeared to inhibit her for much of the season as she struggled for form and consistency. However, Osaka has rediscovered her best game in recent weeks and is on a 11-match winning run, resulting in titles in Osaka and Beijing, beating Barty in the final of the latter.
Osaka has once competed in the WTA Finals, in 2018, but failed to win any of her three round robin matches last year.
Kiki Bertens, who finished 10th in the race to qualify for the eight-player WTA Finals, will fill in as alternative.
The 27-year-old Dutchwoman has made one previous appearance at the WTA Finals, reaching the 2018 semi-finals before losing to eventual champion Elina Svitolina.