
Jack Sock of the United States returns the ball during the first round match against Pierre-Hugues Herbert of France at the Rogers Cup tennis tournament in Montreal, Canada, on Aug. 8, 2017. (Xinhua/Andrew Soong)

Jack Sock of the United States returns the ball during the first round match against Pierre-Hugues Herbert of France at the Rogers Cup tennis tournament in Montreal, Canada, on Aug. 8, 2017. (Xinhua/Andrew Soong)