Dutch top seed Kiki Bertens beat Croatia’s Donna Vekic for the third consecutive time this year with a 7-6 (7-5) 6-2 victory in their round robin match at the WTA Elite Trophy in Zhuhai.
Bertens, playing in her seventh tournament since her US Open third-round exit, was pushed to the limit in an absorbing opening set that lasted an hour and 20 minutes.
There were 15 break points in the match, with Bertens converting four and Vekic winning two.
In the other group, fourth seed Aryna Sabalenka overcame Greek ninth seed Maria Sakkari with a straight sets victory, winning 6-3 6-4.
Belarusian Sabalenka won 86 per cent of her first service points despite making eight double faults and needed only one break of serve in each set to clinch the contest.
American third seed Madison Keys was no match for China’s Zheng Saisai, falling to a 6-4 6-2 defeat.