Belinda Bencic of Switzerland celebrates winning the women's singles round robin match against Petra Kvitova of the Czech Republic at the WTA finals Tennis Tournament in Shenzhen, south China's Guangdong Province, Oct. 29, 2019. (Xinhua/Liang Xu)

Belinda Bencic of Switzerland celebrates winning the women's singles round robin match against Petra Kvitova of the Czech Republic at the WTA finals Tennis Tournament in Shenzhen, south China's Guangdong Province, Oct. 29, 2019. (Xinhua/Liang Xu)

Belinda Bencic of Switzerland celebrates scoring during the women's singles round robin match against Petra Kvitova of the Czech Republic at the WTA finals Tennis Tournament in Shenzhen, south China's Guangdong Province, Oct. 29, 2019. (Xinhua/Liang Xu)

Petra Kvitova of the Czech Republic returns the ball during the women's singles round robin match against Belinda Bencic of Switzerland at the WTA finals Tennis Tournament in Shenzhen, south China's Guangdong Province, Oct. 29, 2019. (Xinhua/Liang Xu)

Belinda Bencic of Switzerland celebrates winning the women's singles round robin match against Petra Kvitova of the Czech Republic at the WTA finals Tennis Tournament in Shenzhen, south China's Guangdong Province, Oct. 29, 2019. (Xinhua/Liang Xu)

Petra Kvitova of the Czech Republic returns the ball during the women's singles round robin match against Belinda Bencic of Switzerland at the WTA finals Tennis Tournament in Shenzhen, south China's Guangdong Province, Oct. 29, 2019. (Xinhua/Liang Xu)

Belinda Bencic of Switzerland returns the ball during the women's singles round robin match against Petra Kvitova of the Czech Republic at the WTA finals Tennis Tournament in Shenzhen, south China's Guangdong Province, Oct. 29, 2019. (Xinhua/Liang Xu)

Belinda Bencic of Switzerland celebrates scoring during the women's singles round robin match against Petra Kvitova of the Czech Republic at the WTA finals Tennis Tournament in Shenzhen, south China's Guangdong Province, Oct. 29, 2019. (Xinhua/Liang Xu)