Serena Williams beats Karolina Pliskova at US Open women's quarterfinal match

Sloane Stephens of the United States reacts after losing a point during the women's singles quarterfinal match against Anastasija Sevastova of Latvia at the 2018 US Open tennis championships in New York, the United States, Sept. 4, 2018. Sevastova won 2-0. (Xinhua/Wang Ying)?