Djokovic, Murray roar into Open quarters

World No. 1 and former champion Novak Djokovic enjoyed a stress-free fourth-round match Tuesday at the U.S. Open, while defending champion Andy Murray shook off a slow start and moved into the quarterfinals.

Djokovic swatted unseeded Marcel Granollers 6-3, 6-0, 6-0 in 1 hour, 19 minutes at Ashe Stadium at the USTA Billie Jean King National Tennis Center. The Serbian star broke Granollers seven times, while the Spaniard was unable to earn a break on Day 9.

"The second and third sets (were) some of the best tennis that I've played on Arthur Ashe in my career," admitted Djokovic. "It's a fantastic feeling when you're playing this well. You love spending time on the court and experiencing such a great zone where you are at that moment."

Djokovic won 25 straight points on his serve to open the match.

The 26-year-old Djokovic has reached at least the quarterfinals in New York every year since 2007 and at least the semis at every major event since Wimbledon in 2010.

The reigning Australian Open champion titled here in 2011 and was the U.S. Open runner-up in 2007, 2010 and last year when he succumbed to Murray in a marquee final. The six-time Grand Slam titlist from Belgrade also lost to Murray in July's Wimbledon finale.

Djokovic's quarterfinal opponent on Thursday will be 21st-seeded Russian Mikhail Youzhny.

Murray, the third seed and the current holder of the U.S. Open, Wimbledon and Olympic titles, ran his record to 17-1 in Grand Slam play this year with a 6-7 (5-7), 6-1, 6-4, 6-4 win over Denis Istomin. Murray had his serve broken twice, as many as he had in his first three matches combined.

Istomin was trying to become the first player from Uzbekistan to reach the quarterfinals in a major.

Ninth-seeded Stanislas Wawrinka of Switzerland advanced through fifth-seeded Tomas Berdych with a 3-6, 6-1, 7-6 (8-6), 6-2 decision. Berdych was a semifinalist here last year, but the Czech was done in by 45 unforced errors.

Next up for Wawrinka is the defending champ.

"I think if I start well, if I stay with him, I can have some good chances to do something," a confident Wawrinka said.

Earlier, the 31-year-old Youzhny came from behind to outlast unseeded former world No. 1 Aussie Lleyton Hewitt 6-3, 3-6, 6-7 (3-7), 6-4, 7-5 in a war of attrition that lasted just under four hours at Armstrong Stadium. Youzhny broke Hewitt's serve 10 times, while the Aussie veteran settled for eight breaks in a tough defeat, one in which he was two points away from victory at one point.

Hewitt had more winners (55-47), more total points won (146-145), and had fewer unforced errors (54-63) than Youzhny, but still exited the draw on Day 9.

The 32-year-old Hewitt pulled off perhaps the biggest upset in the men's draw here by stunning sixth-seeded fellow former Open champ Juan Martin del Potro last week.

Hewitt captured the U.S. Open in 2001 and was the runner-up here in 2004. He also corralled a Wimbledon championship in 2002. The gritty Aussie was trying to reach his first U.S. Open quarterfinal in seven years and first Grand Slam quarter since Wimbledon in 2009.

Youzhny was a U.S. Open semifinalist in 2006 and 2010. He'll now appear in his sixth Grand Slam quarterfinal (2-3).

The men's quarterfinals will commence Wednesday, as second-seeded former No. 1 Rafael Nadal will meet 19th-seeded fellow Spaniard Tommy Robredo and fourth- seeded French Open runner-up David Ferrer of Spain will encounter eighth- seeded Frenchman Richard Gasquet.

Nadal owns 12 major titles, including this year's French Open and the 2010 U.S. Open, where he also finished as a runner-up in 2011.

The amazing Nadal is perfect 19-0 on hardcourts this year.