New York: Chinese fifth seed Li Na and third-seeded Pole Agnieszka Radwanska made the US Open last 16 on Friday as heavyweights Novak Djokovic, Andy Murray and Serena Williams waited in the wings.
Li hit 11 aces in a 6-2, 7-5 victory against teenager Laura Robson, avenging her loss to the Briton at the same stage last year.
The 31-year-old Li, who saw her opponent hit 30 unforced errors and a paltry seven winners, goes on to face either Japanese qualifier Kurumi Nara or Serbian ninth seed Jelena Jankovic, the 2008 runner-up, for a quarter-final spot.
"I was really happy how I was hitting on the court," Li said. "And I thought I served really well."
Robson, 19, had been bothered by a wrist injury in the run-up to the tournament and now has a problem with her teeth.
"I will see my doctor when I get back (about the wrist). I have to get my wisdom teeth taken out, as well," she said.
Li's best US Open performance was a run to the quarter-finals in 2009.
But that is one round better than Radwanska, who has stumbled at the fourth round stage on three occasions.
The 2012 Wimbledon runner-up made the last 16 once again with a 6-4, 7-6 (7/1) win over Russian 32nd seed Anastasia Pavlyuchenkova, a quarter-finalist in 2011.
Pavlyuchenkova, seeded at a major for the first time, was undone by 41 unforced errors, which rendered her 32 winners irrelevant against the steady Radwanska.
Murray, who had to wait until Wednesday night to get his title defense underway, tackles Leonardo Mayer, the Argentine world number 81, for a place in the last 32 after brushing aside French veteran Michael Llodra in his opener.
The third-seeded Scot has played in the finals of the last four Grand Slam tournaments in which he has competed, a run which included a first Wimbledon title last month.
But the British star is taking nothing for granted against Mayer, who made the third round in New York last year.
"He's a very talented player. He's got big sort of long, looping strokes. I think he plays his best tennis on the hard courts. He's very tough," said Murray.
Four-time champion Williams, the top seed, has dropped just four games in her opening two matches and takes on big-hitting Russian-born Kazkhastan player Yaroslava Shvedova, the world number 78, for a last-16 spot.
Williams, chasing a 17th Grand Slam title, has won both their previous meetings in Toronto in 2009 and Wimbledon last year.
Shvedova has twice been a women's doubles champion at the US Open, partnering Vania King to victory in 2010 and 2011.
Djokovic, the 2011 champion and trying to reach the final for a fourth successive season, tackles Benjamin Becker for a place in the third round.
The 87th-ranked German is already part of US Open folklore, having inflicted the last professional defeat of Andre Agassi at the tournament in 2006.
Friday's action also sees two former men's champions clash for a place in the third round when Australia's 2001 winner Lleyton Hewitt meets Argentina's Juan Martin Del Potro, the sixth seed who claimed the 2009 title.
In early men's action Friday, 12th seeded Tommy Haas defeated Lu Yen-Hsun of Taiwan, 6-3, 6-4, 7-6 (7/3).
The 35-year-old German next plays Russian 21st seed Mikhail Youzhny, who saw off Alexandr Dolgopolov of Ukraine 7-5, 6-1, 6-3, for a fourth-round place.