Caroline Wozniaki of Denmark celebrates scoring during the single's quarterfinal match against Angelique Kerber of Germany at the 2018 WTA Qatar Open in Doha, Qatar, on Feb. 16, 2018. Caroline Wozniaki won 2-1. (Xinhua/Nikku)

Angelique Kerber of Germany reacts during the single's quarterfinal match against Caroline Wozniaki of Denmark at the 2018 WTA Qatar Open in Doha, Qatar, on Feb. 16, 2018. Angelique Kerber lost 1-2. (Xinhua/Nikku)