Updated

World No. 1 superstar Novak Djokovic and defending champion Andy Murray were second-round winners Friday, while sixth-seeded Juan Martin del Potro was upended at the U.S. Open.

The 2011 U.S. Open champion handled German Benjamin Becker 7-6 (7-2), 6-2, 6-2 in 1 hour, 51 minutes at Ashe Stadium on the hardcourts at the USTA Billie Jean King National Tennis Center.

"Becker is a quality opponent and he should have won the first set," Djokovic said. "I was fortunate enough to come back and win the first set, and after that, I was much more comfortable on the court."

The six-time Grand Slam titlist Djokovic was last year's runner-up to Murray and also lost in finals here in 2007 and 2010.

Djokovic is the reigning Australian Open champ and was last month's runner-up to Murray at Wimbledon. His third-round opponent will be unheralded Portuguese Joao Sousa.

The third-seeded Murray beat Leonardo Mayer of Argentina by a 7-5, 6-1, 3-6, 6-1 margin. The reigning Wimbledon and U.S. Open titlist beat Djokovic in last year's final in Flushing and was a runner-up here in 2008.

Murray will next do battle with German Florian Mayer, who cruised past American Donald Young 7-5, 6-3, 6-4.

"Yeah, he's very tough," Murray said of his next opponent. "I mean, he comes to net a bit. He has a good slice backhand, but he hits it with two hands, which isn't how remember normally you're taught to play that shot. He has very good feel up at the net. Hits a lot of dropshots."

Del Potro, the 2009 U.S. Open champion, bounced back from a first set misstep to take the second and third sets from former world No. 1 Lleyton Hewitt, but Hewitt outlasted del Potro down the stretch to take a 6-4, 5-7, 3-6, 7-6 (7-2), 6-1 triumph in a marathon match that lasted just over four hours.

Hewitt captured the U.S. Open in 2001 and was the runner-up in 2004.

Fifth-seeded former Wimbledon runner-up Tomas Berdych fired 11 aces in dismissing game American Denis Kudla 7-6 (7-3), 7-6 (7-3), 6-3. The formidable Czech will battle seeded Frenchman Julien Benneteau in his next outing.

Stanislas Wawrinka, the No. 9 seed, discarded Ivo Karlovic of Croatia 7-5, 7-6 (10-8), 6-4. Next up for Wawrinka is Marcos Baghdatis, who took down 17th- seeded South African Kevin Anderson by a 6-2, 6-2, 6-2 margin.

Meanwhile, resurgent 12th-seeded 35-year-old German Tommy Haas took care of Taiwan's Yen-Hsun Lu 6-3, 6-4, 7-6 (7-3). The one-time world No. 2 Haas is a three-time quarterfinalist in Flushing.

In other second-round action involving seeds, No. 20 Andreas Seppi of Italy bested Indian Somdev Devvarman 7-6 (10-8), 6-4, 7-5, No. 21 Russian Mikhail Youzhny mauled Ukrainian Alexandr Dolgopolov 7-5, 6-1, 6-3, and a No. 31 Benneteau topped fellow Frenchman Jeremy Chardy 6-4, 6-3, 6-4. The 31-year-old Youzhny is a two-time U.S. Open semifinalist (2006, 2010) and will meet Haas in the round of 32.

Also on Friday, American Tim Smyczek snuck past Russian Alex Bogomolov Jr. 3-6, 7-6 (8-6), 2-6, 6-4, 6-4; the aforementioned Sousa outlasted Finnish veteran Jarkko Nieminen 1-6, 6-3, 3-6, 6-3, 6-4; Russian Evgeny Donskoy beat German Peter Gojowczyk 6-3, 6-4, 3-6, 4-6, 6-3; Spaniard Marcel Granollers held off American Rajeev Ram 3-6, 4-6, 6-2, 6-3, 7-5; and Uzbekistan's Denis Istomin drubbed German Tobias Kamke 6-4, 6-2, 6-2 at the final Grand Slam event of the year.