ROME (AP) -- Top-ranked Novak Djokovic overcame a poor first set and a smashed racket to beat 14th-seeded Juan Monaco 4-6, 6-2, 6-3 Thursday and reach the Italian Open quarterfinals.
Rafael Nadal routed Marcel Granollers 6-1, 6-1, and the Williams sisters both won. Serena defeated Anabel Medina Garrigues 6-3, 6-1 to extend her winning streak to 16 matches, and Venus upset Samantha Stosur 6-4, 6-3.
With the wind whipping the red-clay surface at the Foro Italico, Djokovic struggled with his serve and backhand in the opening set before settling down and wearing Monaco.
"It was a very strange match. It was difficult to play with that wind. But the conditions were the same for both us, he just handled it better at the start," Djokovic said. "I was playing far too defensively and passively and he was controlling everything. He was the better player for a set and a half."
Djokovic had 22 unforced errors in the first set - including 14 backhands - to Monaco's 16, and got in only 47 percent of his first serves.
When Djokovic missed two consecutive backhands to hand Monaco the first set, he slammed his racket to the clay twice, breaking it on the second attempt, which drew a warning from the chair umpire.
Nadal will meet seventh-seeded Tomas Berdych, who eliminated No. 12 Nicolas Almagro 7-6 (3), 6-3.
Berdych was the runner-up to Roger Federer at last week's Madrid Open on the controversial blue clay.
Also, 16th-seeded Richard Gasquet upset No. 4 Andy Murray 6-7 (1), 6-3, 6-2; and sixth-seeded David Ferrer beat No. 11 Gilles Simon 6-0, 7-6 (5).
Murray skipped the Madrid Open with a back injury, and he said after the loss that it was still bothering him.
Serena Williams called for the trainer while leading 4-1 in the second set and had her left ankle re-taped. She easily won the last two games.
"I wanted to loosen the tape, and so I called the trainer to retape," Serena said. "It was too tight."
With the French Open 10 days away, Serena said she's ready.
"I feel good and I have had a lot of practice on clay," Williams said. "Today I was running so much and I was ready to play and feeling good. I wasn't tired at all."
Serena's quarterfinal opponent will be Italian hope Flavia Pennetta , who routed Petra Cetkovska of the Czech Republic 6-0, 6-1.
For Venus Williams, it was one of her biggest wins since being sidelined six months following the diagnosis of an autoimmune disease, Sjogren's syndrome.
"Every match is a lesson and a challenge for me," she said. "I think that are all great wins nowadays."
Venus will play the winner of the match between defending champion Maria Sharapova and Ana Ivanovic.
Wimbledon champion Petra Kvitova struggled before advancing with a 6-2, 5-7, 6-2 win over Sorana Cirstea of Romania. Her quarterfinal opponent will be Angelique Kerber, who defeated Julia Goerges 6-4, 6-1.
Djokovic eliminated errors from his game in the second set and raised his first-serve percentage. He improved to 6-0 in his career against Monaco.
"It's not the first time and I don't think it will be the last time - I'm a player with a lot of emotion," Djokovic said of breaking his racket. "I hope kids didn't see it. But then it changed the match. ... The momentum swung to my side."
Djokovic won this tournament for the second time last year, part of his memorable 43-match winning streak.