Kei Nishikori of Japan in action against Novak Djokovic of Serbia during the men’s singles final match at the Miami Open tennis tournament on Key Biscayne, Miami, Florida, USA, 03 April 2016. EPA/ERIK S. LESSER

Novak Djokovic of Serbia in action against Kei Nishikori of Japan during the men’s singles final match at the Miami Open tennis tournament on Key Biscayne, Miami, Florida, USA, 03 April 2016. EPA/ERIK S. LESSER

Fans of Kei Nishikori of Japan hold Japanese flag before Nishikori plays against Novak Djokovic of Serbia during the men’s singles final match at the Miami Open tennis tournament on Key Biscayne, Miami, Florida, USA, 03 April 2016. EPA/ERIK S. LESSER

Novak Djokovic of Serbia celebrates after defeating Kei Nishikori of Japan during the men’s singles final match at the Miami Open tennis tournament on Key Biscayne, Miami, Florida, USA, 03 April 2016. EPA/ERIK S. LESSER

Novak Djokovic (R) of Serbia and Kei Nishikori (L) of Japan pose with their trophies after Djokovic defeated Nishikori in the men’s singles final match at the Miami Open tennis tournament on Key Biscayne, Miami, Florida, USA, 03 April 2016. EPA/ERIK S. LESSER

Novak Djokovic of Serbia has his photograph taken with the ball crew after defeating Kei Nishikori of Japan following the men’s singles final match at the Miami Open tennis tournament on Key Biscayne, Miami, Florida, USA, 03 April 2016 EPA/RHONA WISE