Showing the sort of beginning-to-end focus he'll need to win the U.S. Open, top-seeded Novak Djokovic strung together 13 straight games to close out a 6-3, 6-0, 6-0 thrashing of Marcel Granollers on Tuesday and advance to his 18th straight Grand Slam quarterfinal.

"Today, second and third set have been some of the best tennis that I've played on Arthur Ashe in my career," said Djokovic, who has made the final here the last three years and won it in 2011.

"It all comes at a great time for me. It was something I was wishing to be more aggressive as the tournament progresses and to be able to stay committed to play every point, to win every point, regardless of the score."

Next up for Djokovic is a match against 21st-seeded Mikhail Youzhny of Russia, who was two points from defeat but came back to edge two-time major champion Lleyton Hewitt 6-3, 3-6, 6-7 (3), 6-4, 7-5.

While Youzhny and Hewitt slugged out a grueling five-setter, Djokovic needed only 79 minutes to beat Granollers, and had embarrassingly large advantages over the last two sets in points won (50-15) and winners (22-3), and he even won on 21 of 22 moves up to net, which isn't his normal style.

"It's all coming together for me right now," Djokovic said. "I'm aware of the fact that as the tournament goes on I'm going to have bigger challenges, better quality players, higher ranked players, but I'm ready for that challenge. I look forward to it."

The Serb's dominance was mirrored in the women's draw, where top seed Serena Williams trounced Carla Suarez Navarro 6-0, 6-0 — the first 'double-bagel' in a U.S. Open quarterfinals since Martina Navratilova did it in 1989.

"I played really good," Williams said. "I was just more focused than anything. I like to believe there is room for improvement."

Williams' semifinal opponent will be fifth-seeded Li Na, who needed nearly 2½ hours to get past 24th-seeded Ekaterina Makarova of Russia 6-4, 6-7 (5), 6-2.

Li has only won one of nine career matches against Williams.

"Tough, tough opponent," Li said. "But is (a) good challenge to play against her."

The quarterfinals on the other half of the draw are Wednesday: second-seeded Victoria Azarenka of Belarus against the experienced Daniela Hantuchova of Slovakia, and 10th-seeded Roberta Vinci against Flavia Pennetta in a matchup between two Italians in their 30s.

While the other women in that section all advanced Monday, Azarenka's fourth-round match against 2008 French Open champion Ana Ivanovic was postponed until Tuesday because of rain. Azarenka got off to a slow start, but eventually got going and beat the 13th-seeded Ivanovic 4-6, 6-3, 6-4 in a topsy-turvy match with a combined 16 service breaks and 17 double-faults.

Andy Murray shrugged off a poor first-set tiebreaker to beat Denis Istomin 6-7 (5), 6-1, 6-4, 6-4 on Tuesday to advance to the quarterfinals of the U.S. Open for the third-straight year.

The defending champion came apart after leading 5-3 in the opening-set tiebreaker.

First, Istomin hit a forehand winner to close a 27-shot exchange. Then Murray, distracted before his service toss by a shout from the stands, double-faulted. A forehand into the net gave Istomin a set point and the Uzbek took the set when Murray pushed a backhand wide.

Istomin was broken right away in the second set and, aside from winning a point with a no-look between-the-legs shot in the last game, there were few highlights as the match was squared at one set all.

There was more shakiness from Murray in the third set, in which he went up a break, only to lose serve to make it 3-3. But he broke right back for a 4-3 edge, and was back on his way to a victory that improved his record over his past five Grand Slam tournaments to 30-2.

His opponent in the last eight will be Stanislas Wawrinka, who reached his second U.S. Open quarterfinal by eliminating Tomas Berdych 3-6, 6-1, 7-6 (6), 6-2.

Murray leads the head-to-head series against Wawrinka 8-5, but they've split their two previous meetings on the U.S. Open's hard courts: Murray won in 2008, and Wawrinka won two years later. Wawrinka also won their only match this season, 6-1, 6-2 on red clay at Monte Carlo in April.

"He's very tough. Very talented," Murray said. "We played once on this court when we were much younger. But a lot has changed since then."