MIAMI GARDENS, Fla. -- Novak Djokovic pulled a spare ball from his pocket, angrily whacked it against the backstop and pounded his uncooperative racket into the concrete.
He lost his temper but not the match. Annoyed after squandering a second-set lead, Djokovic regrouped and beat Federico Delbonis 7-5, 4-6, 6-1 on Sunday in the third round of the Miami Open.
Djokovic appeared on his way to an easy victory when he led 3-1 in the second set, but he dropped serve twice in a row. He then steadied himself to win a succession of long rallies and sweep the last five games.
"We were very close in the beginning of the third set,'' he said. "It could have gone a different way.''
The top-ranked Djokovic is trying for his seventh title at the Miami Open, which moved this year to the Dolphins' complex.
Defending champion John Isner was broken in the first game but held the rest of the way and hit 16 aces to beat Albert Ramos-Vinolas 7-5, 7-6 (6).
Isner, now 33, won the biggest title of his career in the tournament a year ago. Seeded No. 7, he'll next face No. 19 Kyle Edmund, who beat No. 12 Milos Raonic 6-4, 6-4.
Djokovic's fourth-round opponent will be No. 22 Roberto Bautista Agut, who eliminated No. 15 Fabio Fognini 6-4, 6-4.
"I'm hitting the ball well,'' Djokovic said. "I just need a little more consistency to hold that level of play the entire match.''
Crowds on the outer courts were again large and festive, but the atmosphere in the vast stadium was more subdued, with the stands only half full for Djokovic's match.
"It's a unique stadium in tennis,'' he said. "It's obviously different from anything we've experienced before. It's not a tennis venue. We're guests here of the Miami Dolphins.''
The Associated Press contributed to this report.