World no. 3 Naomi Osaka has withdrawn from the WTA Finals after just one match, struggling with a right shoulder injury that ended her season earlier than she expected. World no. 10 Kiki Bertens will replace the Japanese in the Red Group who will now face Ashleigh Barty in the first match of Tuesday's program.
On Sunday, Naomi Osaka grabbed the first victory at this event after a 7-6, 4-6, 6-4 triumph over Petra Kvitova in two hours and 30 minutes. It was their second clash after the memorable final of the Australian Open in January and the second victory for the young Japanese against the most experienced rival in the draw, with Kvitova making her seventh WTA Finals appearance.
Petra had 40 winners but also 40 unforced errors, playing some loose forehands in the pivotal moments and failing to make the points shorter or produce more damage on the return. Osaka fended off nine out of 14 break chances she played against, earning five breaks from eight opportunities and taking only two points more than Kvitova in the end thanks to a double break in the deciding set.
The Czech made a flying start, notching three powerful holds and earning a break in the first game of the match with a smash winner. An ace pushed Petra 2-0 up and there were more break chances up for grabs in the third game, having the opportunity to forge an even bigger advantage.
Osaka fended off those to remain within one break deficit, with that game becoming even more critical when the Japanese broke back in game eight after taking four straight points to level the score at 4-4. The Czech had a chance to go in front again in game nine, squandering three break points and losing the tie break 7-1 after a terrible return to hand the set to her rival despite having more chances.
They traded four breaks in the opening six games of the second set and this time it was Kvitova who had the upper hand in the closing moments, securing the third break in game ten following a loose backhand from Osaka and forcing the decider.
Starting all over, Osaka broke in the third game and extended the lead at 4-2 when Petra sprayed a volley error, moving a game away from the victory. The Czech fended off two match points in the eighth game, pulling one break back after forcing a mistake from Naomi and reducing the deficit to 5-4.
There were no errors from Osaka in the tenth game, though, hitting a service winner for a hold at 15 and the first win at this tournament in her career, hoping for more of the same in the remaining encounters in the Red Group.
"I'm disappointed to have to withdraw from the Finals," Osaka said. "It has been a great event in Shenzhen, and it's the biggest WTA event of the year. 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."