Polona Hercog of Slovenia celebrates after winning the qualifying match against Sabina Sharipova of Uzbekistan at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Polona Hercog won 2-0 to enter the final round of qualifying. (Xinhua/Nikku)

Polona Hercog of Slovenia serves during the qualifying match against Sabina Sharipova of Uzbekistan at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Polona Hercog won 2-0 to enter the final round of qualifying. (Xinhua/Nikku)

Sabina Sharipova of Uzbekistan hits a return during the qualifying match against Polona Hercog of Slovenia at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Sabina Sharipova lost 0-2. (Xinhua/Nikku)

Polona Hercog of Slovenia hits a return during the qualifying match against Sabina Sharipova of Uzbekistan at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Polona Hercog won 2-0 to enter the final round of qualifying. (Xinhua/Nikku)

Karolina Muchova of the Czech Republic serves during the qualifying match against Kristyna Pliskova of the Czech Republic at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Karolina Muchova won 2-1 to enter the final round of qualifying. (Xinhua/Nikku)

Kristyna Pliskova of the Czech Republic hits a return during the qualifying match against Karolina Muchova of the Czech Republic at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Kristyna Pliskova lost 1-2. (Xinhua/Nikku)

Shuko Aoyama of Japan reacts during the qualifying match against Ajla Tomljanovic of Australia at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Shuko Aoyama lost 1-2. (Xinhua/Nikku)

Shuko Aoyama of Japan hits a return during the qualifying match against Ajla Tomljanovic of Australia at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Shuko Aoyama lost 1-2. (Xinhua/Nikku)

Karolina Muchova of the Czech Republic serves during the qualifying match against Kristyna Pliskova of the Czech Republic at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Karolina Muchova won 2-1 to enter the final round of qualifying. (Xinhua/Nikku)

Kristyna Pliskova of the Czech Republic hits a return during the qualifying match against Karolina Muchova of the Czech Republic at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Kristyna Pliskova lost the match by 1-2. (Xinhua/Nikku)

Shuko Aoyama of Japan hits a return during the qualifying match against Ajla Tomljanovic of Australia at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Shuko Aoyama lost 1-2. (Xinhua/Nikku)

Karolina Muchova of the Czech Republic celebrates after winning the qualifying match against Kristyna Pliskova of the Czech Republic at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Karolina Muchova won 2-1 to enter the final round of qualifying. (Xinhua/Nikku)

Shuko Aoyama of Japan hits a return during the qualifying match against Ajla Tomljanovic of Australia at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Shuko Aoyama lost 1-2. (Xinhua/Nikku)

Ajla Tomljanovic of Australia hits a return during the qualifying match against Shuko Aoyama of Japan at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Ajla Tomljanovic won 2-1 to enter the final round of qualifying. (Xinhua/Nikku)

Madison Brengle of the United States hits a return during the qualifying match against Zhu Lin of China at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Zhu Lin won 2-0 to enter the final round of qualifying. (Xinhua/Nikku)

Shuko Aoyama of Japan hits a return during the qualifying match against Ajla Tomljanovic of Australia at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Shuko Aoyama lost 1-2. (Xinhua/Nikku)

Madison Brengle of the United States hits a return during the qualifying match against Zhu Lin of China at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Zhu Lin won 2-0 to enter the final round of qualifying. (Xinhua/Nikku)

Ajla Tomljanovic of Australia reacts during the qualifying match against Shuko Aoyama of Japan at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Ajla Tomljanovic won 2-1 to enter the final round of qualifying. (Xinhua/Nikku)

Ajla Tomljanovic of Australia hits a return during the qualifying match against Shuko Aoyama of Japan at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Ajla Tomljanovic won 2-1 to enter the final round of qualifying. (Xinhua/Nikku)

Ajla Tomljanovic of Australia hits a return during the qualifying match against Shuko Aoyama of Japan at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Ajla Tomljanovic won 2-1 to enter the final round of qualifying. (Xinhua/Nikku)

Madison Brengle of the United States hits a return during the qualifying match against Zhu Lin of China at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Zhu Lin won 2-0 to enter the final round of qualifying. (Xinhua/Nikku)

Angelique Kerber of Germany attends a press conference ahead of the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. (Xinhua/Nikku)

Elina Svitolina of Ukraine attends a press conference ahead of the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. (Xinhua/Nikku)

Madison Brengle of the United States serves during the qualifying match against Zhu Lin of China at the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. Zhu Lin won 2-0 to enter the final round of qualifying. (Xinhua/Nikku)

Angelique Kerber of Germany attends a press conference ahead of the 2019 WTA Qatar Open in Doha, Qatar, on Feb. 10, 2019. (Xinhua/Nikku)