MASON, OH - AUGUST 18: Marin Cilic of Croatia serves during his match against Novak Djokovic of Serbia during Day 8 of the Western & Southern Open at Lindner Family Tennis Center on August 18, 2018 in Mason, Ohio. (Photo by Joe Robbins/Getty Images)
MASON, OH - AUGUST 18: Marin Cilic of Croatia serves during his match against Novak Djokovic of Serbia during Day 8 of the Western & Southern Open at Lindner Family Tennis Center on August 18, 2018 in Mason, Ohio. (Photo by Joe Robbins/Getty Images)