WASHINGTON, DC - AUGUST 03: Kei Nishikori of Japan celebrates a point against Alexander Zverev of Germany during Day Seven of the Citi Open at the Rock Creek Tennis Center on August 3, 2018 in Washington, DC. (Photo by Mitchell Layton/Getty Images)
WASHINGTON, DC - AUGUST 03: Kei Nishikori of Japan celebrates a point against Alexander Zverev of Germany during Day Seven of the Citi Open at the Rock Creek Tennis Center on August 3, 2018 in Washington, DC. (Photo by Mitchell Layton/Getty Images)