Jessica Pegula of the United States returns the ball during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)

Naomi Osaka of Japan serves during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)

Naomi Osaka of Japan serves during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)

Naomi Osaka of Japan returns the ball during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)

Naomi Osaka of Japan returns the ball during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)

Naomi Osaka of Japan returns the ball during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)

Jessica Pegula of the United States returns the ball during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)

Jessica Pegula of the United States returns the ball during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)

Naomi Osaka of Japan returns the ball during the women's singles first round match between Naomi Osaka of Japan and Jessica Pegula of the United States at the 2019 China Open tennis tournament in Beijing, capital of China, Sept. 29, 2019. (Xinhua/Jia Haocheng)