Petra Kvitova of the Czech Republic returns a shot during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova of the Czech Republic returns a shot during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Aryna Sabalenka of Belarus celebrates after the women's singles second round match between Aryna Sabalenka of Belarus and Danielle Collins of the United States at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Aryna Sabalenka of Belarus returns a shot during the women's singles second round match between Aryna Sabalenka of Belarus and Danielle Collins of the United States at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Aryna Sabalenka of Belarus celebrates after the women's singles second round match between Aryna Sabalenka of Belarus and Danielle Collins of the United States at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova of the Czech Republic greets spectators after the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Aryna Sabalenka of Belarus returns a shot during the women's singles second round match between Aryna Sabalenka of Belarus and Danielle Collins of the United States at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova of the Czech Republic returns a shot during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Aryna Sabalenka of Belarus celebrates after the women's singles second round match between Aryna Sabalenka of Belarus and Danielle Collins of the United States at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Polona Hercog of Slovenia returns a shot during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova of the Czech Republic serves during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova of the Czech Republic celebrates after the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova of the Czech Republic returns a shot during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Polona Hercog of Slovenia returns a shot during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova of the Czech Republic celebrates during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Polona Hercog of Slovenia serves during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova of the Czech Republic returns a shot during the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)

Petra Kvitova (L) of the Czech Republic shakes hands with Polona Hercog of Slovenia after the women's singles second round match between Petra Kvitova of the Czech Republic and Polona Hercog of Slovenia at the 2019 WTA Wuhan Open tennis tournament in Wuhan of central China's Hubei Province, Sept. 23, 2019. (Xinhua/Cheng Min)