The Australian Open champion won all 21 of his first service points to beat Guillermo Garcia-Lopez 6-1, 6-2 and advance to the quarterfinals, where he was joined by fellow third-round winner Roger Federer and top-ranked Rafael Nadal, who advanced after opponent Juan Martin del Potro withdrew with a hip injury.

Fourth-ranked Andy Murray failed to join them after he lost to hard-hitting Brazilian Thomaz Bellucci 6-4, 6-2.

Djokovic, who is 31-0 since last year's Davis Cup final, is tied for third with Ivan Lendl for the best season start since 1980. John McEnroe won 42 straight to start the 1984 season, and Bjorn Borg won 33 in a row at the beginning of the 1980 season.

"I know I'm playing great now but there is always something you can improve on - you can never be perfect," the Serbian player said. "I'm winning service games comfortably.

That's something I'm happy about today and an encouraging fact for upcoming matches, especially on clay." Djokovic will surpass Lendl's 1986 mark if he wins Friday's quarterfinal against David Ferrer or Sergiy Stakhovsky.

While the men's favorites all advanced to the last eight, top-ranked woman Caroline Wozniacki was upset by Julia Goerges for the second straight tournament as she exited at the third round 6-4, 1-6, 6-3. French Open champion Francesca Schiavone also bowed out.

Third-seeded Federer recovered from Wednesday's struggle against Feliciano Lopez to get past Xavier Malisse of Belgium 6-4, 6-3.

"Mentally I had to shift a bit. I just wanted to put in a good performance, which is what I did," said Federer, in control after having to save a match point against Lopez one night earlier. "It was a quick turnaround. I just had to get past this match today to have the quarters in sight." Federer plays Robin Soderling on Friday after the Swede emerged as a 7-6 (8), 7-5 winner in a tight match against Jo-Wilfried Tsonga.

Meanwhile, Murray was visibly frustrated by being unable to match Bellucci's quality as the Brazilian blazed four aces to help save all three of Murray's break points. The 36th-ranked Bellucci broke Murray on all three opportunities, including on match point when Murray netted.

Bellucci plays seventh-seeded Czech Tomas Berdych next.

Del Potro pulled out after feeling discomfort in his left hip. With his participation at the French Open at stake, Del Potro preferred not to risk another injury as he rediscovers his form after wrist surgery sidelined him for most of last year.

"It's not nice to have to withdraw from this tournament and this game which would have been nice to play but I'm not in shape," said the 32nd-ranked Argentine, who dropped to as low as No. 481 in January before winning in Delray Beach and Estoril. "I tried but I'm not in shape to play."

Earlier, the 27th-ranked Goerges broke Wozniacki in the eighth game of the deciding set to lead 5-3 before serving out the match.

"The second set she started to be more aggressive and I started to get tired, so I said to myself keep yourself together for the third set and try to fight for every point," said the German, who beat Wozniacki in the Porsche Grand Prix final in Stuttgart, Germany, on April 24.

Goerges plays Anastasia Pavyluchenkova in the last eight after the Russian dismissed fifth-seeded Sam Stosur 7-6 (4), 6-3.

Bethanie Mattek-Sands secured the biggest win of her career as the 41st-ranked American knocked the third-seeded Schiavone out 7-6 (5), 6-3.

Mattek-Sands - sporting knee-high socks to match the thick stroke of black eyeliner under her eyes - will next play Australian Open finalist Li Na after the Chinese player rallied to beat Roberta Vinci of Italy 2-6, 6-2, 6-1.

"I'm really happy with my play on clay right now," Mattek-Sands said. "I feel like a true dirtballer." Fourth-seeded Victoria Azarenka of Belarus dispatched Spanish wild card Arantxa Parra Santonja 6-0, 6-3 to set up a match with fellow winner Lucie Safarova.