Williams, Djokovic Advance at Miami Open

Eight-time champion Serena Williams avoided the upset bug at the Miami Open on Saturday, reaching the fourth round by beating Zarina Diyas 7-5, 6-3.

The South Floridian seemed unfazed by the subtropical heat, earning her 20th consecutive victory at Key Biscayne. Earlier Saturday, Rafael Nadal retired from a match for the first time in six years as temperatures approached 90 degrees and were even higher on the sunbaked stadium hardcourt.

"I live down the street, and I'm used to these conditions," Williams said. "Even though it was a little humid, I'm used to it and I love this weather.

"Rafa played like an hour-and-a-half, two hours before me, so that makes a huge difference. So I think that he was in the most intense part of the sun, whereas I was kind of at tail end of it. But I was fine."

Next up for Williams is a date with veteran Svetlana Kuznetsova, who beat Caroline Garcia in a third-set tiebreaker 4-6, 6-2, 7-6 (6).

"It's a great matchup," Williams said of Kuznetsova. "She plays well and makes a lot of the great shots. She's actually been playing well this year. She had a couple big wins and couple good tournaments.

 Novak Djokovic was chasing a shot in his forehand corner when his left foot gave way and he tumbled to the court, landing on his left side as his racket went flying.

He lost the point, the game and his serve, making it 4-all in the first set. But the collision with the concrete gave his game a needed jolt, and he quickly rose to pull away and beat Joao Sousa 6-4, 6-1 on Sunday in the third round at the Miami Open.

In the first game after he fell, Djokovic cracked several forehands more forceful than what he had previously offered. He broke for a 5-4 lead and lost only 11 points in the final eight games.

Djokovic said he slipped on a wet spot and wasn't concerned that he had hurt himself. But he was worried about beating Sousa.

"That first set went down to a few points," Djokovic said. "After that it was quite a good performance. He made me push myself harder in the second set."

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.