Djokovic beats Delbonis in 3rd round at Miami Open

Novak Djokovic, of Serbia, returns to Federico Delbonis, of Argentina, during the Miami Open tennis tournament, Sunday, March 24, 2019, in Miami Gardens, Fla. (AP Photo/Lynne Sladky)

John Isner of USA, returns a volley to Albert Ramos-Vinglas of Spain, during the Miami Open tennis tournament, Sunday, March 24, 2019, in Miami Gardens, Fla. (AP Photo/Joel Auerbach)

Simona Halep, of Romania, serves to Polona Hercog, of Slovenia, during the Miami Open tennis tournament, Sunday, March 24, 2019, in Miami Gardens, Fla. (AP Photo/Lynne Sladky)

John Isner returns a volley to Albert Ramos-Vinglas, of Spain, during the Miami Open tennis tournament, Sunday, March 24, 2019, in Miami Gardens, Fla. (AP Photo/Joel Auerbach)

Daniella Collins reacts during her match against Yafan Wang, of China, during the Miami Open tennis tournament, Sunday, March 24, 2019, in Miami Gardens, Fla. (AP Photo/Lynne Sladky)

Novak Djokovic, of Serbia, celebrates after his match against Federico Delbonis, of Argentina, during the Miami Open tennis tournament, Sunday, March 24, 2019, in Miami Gardens, Fla. Djokovic won 7-5, 4-6, 6-1. (AP Photo/Lynne Sladky)