South Korea's Kim Ga Eun celebrates during the women's singles 2nd round match against China's Cai Yanyan at the BWF World Championships 2019 in Basel, Switzerland, Aug. 21, 2019. (Xinhua/Li Jundong)

China's Cai Yanyan reacts during the women's singles 2nd round match against South Korea's Kim Ga Eun at the BWF World Championships 2019 in Basel, Switzerland, Aug. 21, 2019. (Xinhua/Li Jundong)

South Korea's Kim Ga Eun celebrates during the women's singles 2nd round match against China's Cai Yanyan at the BWF World Championships 2019 in Basel, Switzerland, Aug. 21, 2019. (Xinhua/Li Jundong)

South Korea's Kim Ga Eun returns the shuttle during the women's singles 2nd round match against China's Cai Yanyan at the BWF World Championships 2019 in Basel, Switzerland, Aug. 21, 2019. (Xinhua/Li Jundong)

South Korea's Kim Ga Eun returns the shuttle during the women's singles 2nd round match against China's Cai Yanyan at the BWF World Championships 2019 in Basel, Switzerland, Aug. 21, 2019. (Xinhua/Li Jundong)

China's Cai Yanyan returns the shuttle during the women's singles 2nd round match against South Korea's Kim Ga Eun at the BWF World Championships 2019 in Basel, Switzerland, Aug. 21, 2019. (Xinhua/Li Jundong)

China's Cai Yanyan competes during the women's singles 2nd round match against South Korea's Kim Ga Eun at the BWF World Championships 2019 in Basel, Switzerland, Aug. 21, 2019. (Xinhua/Li Jundong)

China's Cai Yanyan reacts during the women's singles 2nd round match against South Korea's Kim Ga Eun at the BWF World Championships 2019 in Basel, Switzerland, Aug. 21, 2019. (Xinhua/Li Jundong)