KEY BISCAYNE, FL - MARCH 24: Kei Nishikori of Japan returns a shot against Kevin Anderson of South Africa during day 5 of the Miami Open at Crandon Park Tennis Center on March 24, 2017 in Key Biscayne, Florida. (Photo by Al Bello/Getty Images)

KEY BISCAYNE, FL - MARCH 24:  Kei Nishikori of Japan returns a shot against Kevin Anderson of South Africa during day 5 of the Miami Open at Crandon Park Tennis Center on March 24, 2017 in Key Biscayne, Florida.  (Photo by Al Bello/Getty Images)