New York - World number one Novak Djokovic raced into the US Open quarter-finals for the loss of just three games on Tuesday while defending champion Andy Murray was again involved in a four-set duel.
Top seeded Djokovic, the 2011 champion, wrapped up a place in his 18th successive Grand Slam quarter-final when he crushed Spanish world number 43 Marcel Granollers 6-3, 6-0, 6-0 in just 79 minutes.
Andy Murray, the third seed, reached the quarter-finals for a third successive year with a 6-7 (5/7), 6-1, 6-4, 6-4 win over Denis Istomin, the 64th-ranked Uzbek.
Djokovic will next tackle Russian 21st seed Mikhail Youzhny, a semi-finalist in 2006 and 2010, over whom he has a 5-3 career lead.
Youzhny carved out a four-hour, 6-3, 3-6, 6-7 (3/7), 6-4, 7-5 win over 2001 champion Lleyton Hewitt after trailing 4-1 in the fourth set and 5-2 in the fifth.
Swiss ninth seed Stanislas Wawrinka reached the last eight by eliminating Czech fifth seed Tomas Berdych, a semi-finalist last year, 3-6, 6-1, 7-6 (8/6), 6-2.
Wawrinka will now face Murray for a place in the last four, trailing 8-5 in their series, although he did win their 2010 US Open third-round meeting.
Djokovic, bidding to make the final for a fourth successive year, hit 34 winners and faced just one break point against Granollers, one of four Spaniards in the last 16.
But Granollers' challenge had already been fatally undermined by having played three five-set matches and spending almost 10 hours on court, twice as long as Djokovic, who has yet to lose a set.
"I definitely played one of the best matches that I've played in my life here at the Arthur Ashe Stadium," Djokovic said after winning the last 15 games of the one-sided tie.
"It was 3-all in the first set and then I managed to get the right advantage and I played flawless tennis."
He also won the first 25 points in a row on his serve to start the match.
"This is probably the first time I've experienced something like that. I can't say I have one of the strongest serves on the tour but I served pretty well."
The 26-year-old Murray took his record in the majors this year to 17-1 with his second win of 2013 over Istomin after also seeing off the Uzbek player on his way to the Brisbane title in January.
Istomin, who has been coached by his mother Klaudiya since his junior days, sported a bright orange shirt for the encounter and he had Murray dazzled in the first set.
"It was tough with a strong breeze and we both struggled with our timing," said Murray.
"I tried to dictate the points after the first set when I had the wind with me and use my forehand more."
Meanwhile, on the same Louis Armstrong court which had swallowed up five-time champion Roger Federer the day before, Youzhny celebrated just his second win in seven meetings over Hewitt.
The 32-year-old Hewitt, the oldest man left in the tournament, was bidding to make the last-eight in New York for the first time since 2006, having defeated 2009 champion Juan Martin Del Potro in the second round.
But he was left to rue his failure to serve out the match at 5-3 in the decider after having recovered from losing the first set and being a break down in the second.
"It could have gone either way. There were lots of changes in momentum. It was hard for both of us to hold serve but he played the big games when he needed to," said Hewitt.
"He didn't give many cheap errors. I left it all out there. I don't have any regrets."
Youzhny, who famously defeated Rafael Nadal in the fourth round in 2006, hit 47 winners while committing 63 unforced errors with Hewitt, now the world number 66, finished with 55 winners and 54 unforced errors.
However, he served up nine double faults at crucial times in his 200th Grand Slam match, which proved a dramatic affair with even a 46-shot rally being exchanged in the third set.
"It was a great atmosphere and a joy to play. I fought back in the fourth and fifth sets because I didn't want to be heading home just yet," said 31-year-old Youzhny.
US Open results on Tuesday (x denotes seeded player):
Novak Djokovic (SRB x1) bt Marcel Granollers (ESP) 6-3, 6-0, 6-0
Mikhail Youzhny (RUS x21) bt Lleyton Hewitt (AUS) 6-3, 3-6, 6-7 (3/7), 6-4, 7-5
Stanislas Wawrinka (SUI x9) bt Tomas Berdych (CZE x5) 3-6, 6-1, 7-6 (8/6), 6-2
Andy Murray (GBR x3) bt Denis Istomin (UZB) 6-7 (5/7), 6-1, 6-4, 6-4
Serena Williams (USA x1) bt Carla Suarez Navarro (ESP x18) 6-0, 6-0
Li Na (CHN x5) bt Ekaterina Makarova (RUS x24) 6-4, 6-7 (5/7), 6-2
Victoria Azarenka (BLR x2) bt Ana Ivanovic (SRB x13) 4-6, 6-3, 6-4
Leander Paes/Radek Stepanek (IND/CZE x4) bt Aisam-ul-Haq Qureshi (PAK)/Jean-Julien Rojer (PAK/NED x5) 6-1, 6-7 (3/7), 6-4
Alexander Peya/Bruno Soares (AUT/BRA x2) bt Jamie Murray/John Peers (GBR/AUS) 6-4, 6-7 (4/7), 6-4
Ekaterina Makarova/Elena Vesnina (RUS/RUS x2) bt Cara Black/Marina Erakovic (ZIM/NZL x13) 5-7, 6-2, 6-4
Anabel Medina Garrigues/Bruno Soares (ESP/BRA x5) bt Lucie Hradecka/Frantisek Cermak (CZE/CZE) 6-4, 6-7 (3/7), 13-11
Abigail Spears/Santiago Gonzalez (USA/MEX) bt Liezel Huber/Marcelo Melo (USA/BRA x8) 2-6, 6-1, 11-9
Kristina Mladenovic/Daniel Nestor(FRA/CAN) bt Chan Hao-Ching/Martin Emmerich (TPE/GER) 7-6 (7/5), 6-3