MASON, OH - AUGUST 19: Borna Coric of Croatia hits a return shot to Marin Cilic of Croatia during a quarterfinal match on Day 7 of the Western & Southern Open at the Lindner Family Tennis Center on August 19, 2016 in Mason, Ohio. Coric retired after Cilic won the first set 6-2. (Photo by Joe Robbins/Getty Images)
