New York - Agnieszka Radwanska's US Open woes continued Wednesday as China's Peng Shuai toppled the fourth-seeded Pole 6-3, 6-4 to reach the third round.
Radwanska, a former Wimbledon finalist who counts this year's Australian Open among two other Grand Slam semi-final appearances, had hoped to make it past the fourth round at Flushing Meadows in her ninth attempt.
But the 39th-ranked Peng put paid to that, breaking Radwanska three times en route to the victory sealed with a backhand winner on her third match point -- her 28th winner of the contest.
"She's tough to play," said Peng, who beat Radwanska at the same stage of the US Open in 2010. "I kept running, I fought. It was amazing.
"I will try to keep going," said Peng, whose best prior US Open showing was a round of 16 appearance in 2011.
Although Peng has failed to lift a trophy in six WTA finals appearances, she has tasted victory in doubles.
In February she became the first Chinese player to reach number one in the world when she went top of the doubles charts thanks to her success with Taiwan partner Hsieh Su-Wei.
In other early action, French 22nd seed Alize Cornet dismissed Slovakia's Daniela Hantuchova 6-3, 6-3 to reach the third round -- matching her best US Open run.
Hantuchova had won six of their nine prior encounters, including at the 2012 Olympic tournament.
But Cornet controlled this one, breaking Hantuchova four times en route to the victory in an hour and 22 minutes.
Former champion Maria Sharapova, who won her fifth Grand Slam title at Roland Garros this year, was also trying to book her third-round berth on Wednesday, taking on Alexandra Dulgheru.
Sharapova, seeded fifth, has won both of her previous meetings with the 95th-ranked Romanian.
With top seed and two-time defending champion Serena Williams having a day off, world number two Simona Halep was the top seed in action.
The second-seeded Romanian, runner-up to Sharapova at the French Open, faced Slovakia's Jana Cepelova.
The biggest names of the men's field -- Novak Djokovic, Roger Federer and Andy Murray also had Wednesday off.
Australian Open winner Stan Wawrinka, the third seed from Switzerland, headlined the night session, taking on Brazil's Thomaz Bellucci in one of two men's second-round matches on the slate.
Wawrinka's triumph in Melbourne broke a streak of 16 straight Grand Slam titles won by tennis' Big Four of Rafael Nadal, Djokovic, Federer and Murray.
That major breakthrough was followed by a first-round exit at the French Open and a first quarter-final appearance at Wimbledon.
Former champion Lleyton Hewitt was among 32 men trying to secure their second-round berths on Wednesday.
Hewitt, 33, has nabbed two titles this year, but faced a tough first-round clash with sixth-seeded Czech Tomas Berdych, who is trying to win his 100th career Grand slam match.
Seventh-seeded Bulgarian Grigor Dimitrov, trying to win his first US Open match after first-round exits the past three years, takes on US wildcard Ryan Harrison.
Dimitrov, at 23 the youngest player among the world's top 10, has won three ATP titles this season. He became the first Bulgarian man to reach the quarter-finals of a major at the Australian Open, and after a first-round shock at Roland Garros reached the semi-finals at Wimbledon.
Croatia's Marin Cilic, who reached his first Grand Slam quarter-final at Wimbledon, takes on 2006 Australian Open finalist Marcos Baghdatis.
Results on Wednesday from the third day of the US Open, the final Grand Slam tournament of 2014 (x denotes seeded player):
Feliciano Lopez (ESP x19) bt Ivan Dodig (CRO) 1-6, 7-5, 2-6, 6-4, 1-1 - retired
Marin Cilic (CRO x14) bt Marcos Baghdatis (CYP) 6-3, 3-1 - retired
Belinda Bencic (SUI) bt Kurumi Nara (JPN x31) 6-4, 4-6, 6-1
Johanna Larsson (SWE) bt Sloane Stephens (USA) 5-7, 6-4, 6-2
Alize Cornet (FRA x22) bt Daniela Hantuchova (SVK) 6-3, 6-3
Roberta Vinci (ITA x28) bt Irina Begu (ROM) 2-6, 6-4, 6-1
Peng Shuai (CHN) bt Agnieszka Radwanska (POL x4) 6-3, 6-4