‚Äč‚ÄčNovak Djokovic took a nasty spill during a tight first set but then pulled away and beat Joao Sousa 6-4, 6-1 Sunday in the third round at the Miami Open in Key Biscayne, Fla.

Djokovic slipped and fell on his left side behind the baseline as he hit a running forehand into the net to lose serve, making the score 4-all. But he rose unhurt and soon took charge of the match, losing only 11 points in the final eight games.

"The first set was very close," Djokovic said. "It could have gone either way. I played well in the right moments."

Seeded No. 1, Djokovic is bidding for his sixth Key Biscayne championship, which would tie Andre Agassi's men's record. Serena Williams is seeking her ninth title.

Djokovic improved to 24-1 this year, and he's 38-5 lifetime at Key Biscayne.

Sousa, seeded 33rd, has lost 19 matches in a row when playing top-10 opponents.

In other men's play, No. 7 Tomas Berdych erased all 10 break points he faced and defeated American Steve Johnson 6-3, 6-7 (6), 6-3. Johnson, seeded 31st, fell to 0-13 against top-10 opponents.

Richard Gasquet, seeded 10th, eliminated No. 20 Benoit Paire in an all-French matchup, 6-3, 6-0. No. 14 Dominic Thiem advanced to the round of 16 against Djokovic by beating qualifier Yoshihito Nishioka 6-2, 6-2.

Kerber's opponent retires

Second seed Angelique Kerber advanced to the fourth round when Dutch qualifier Kiki Bertens was forced to retire in the third set on Sunday.

Bertens dominated the world number three in the opening set, but the 24-year-old became unwell early in the second set and was forced to take a medical timeout.

She eventually retired with an illness in the final set to hand Kerber a 1-6 6-2 3-0 win on another steamy day in south Florida.

Meanwhile, two-time champion Victoria Azarenka overcame five double-faults and held every service game to beat qualifier Magda Linette 6-3, 6-0. Azarenka, seeded 13th, moved into the fourth round and is bidding to become only the third woman to win Indian Wells and Miami back to back.

Floridian Madison Keys, seeded No. 22, reached the round of 16 for the first time in seven tournament appearances by beating No. 9 Roberta Vinci 6-4, 6-4. Keys won 19 of 21 points at the net.

With files from Reuters