Philipp Kohlschreiber of Germany returns the ball at the US Open in New York

Philipp Kohlschreiber of Germany returns the ball to Kei Nishikori of Japan in the first set of their fourth round match in the Louis Armstrong Stadium at the 2018 US Open Tennis Championships at the USTA Billie Jean King National Tennis Center in New York City on September 3, 2018. Nishikori won 6-3, 6-3, 7-5. Photo by Monika Graff/UPI