New York: Second seed Agnieszka Radwanska was ousted from the US Open tennis tournament after she lost 1-6, 4-6 to 20th seeded Italian Roberta Vinci in the women`s singles here at the Flushing Meadows.
Vinci entered a Grand Slam quarterfinal for the first time Monday.
The victory gave the Italian a showdown against her doubles partner Sara Errani, seeded 10th, who defeated German Angelique Kerber 7-6 (5), 6-3.
The Italian duo, who won the Roland Garros this year, are still alive in doubles reaching the quarterfinals as the No.2 seeds.
"Our friendship is one thing that helps very much on the court. But also because we both are playing very good especially this year," said Errani.
Kerber was a semifinalist here last year.
Kerber double-faulted at the end of the first-set tie-breaker. She had 38 unforced errors.
Radwanska was trying to become the first Polish woman to reach the quarterfinals here in the Open era. She had a 4-0 head-to-head record against Vinci prior to this encounter.
Serena Williams didn`t drop a game while advancing to the quarterfinals.
She beat 82nd-ranked Andrea Hlavackova 6-0, 6-0 in 57 minutes. It was the first time in her 62 career victories at Flushing Meadows that the three-time US Open champion enjoyed a "double bagel".
Williams had 31 winners and just seven unforced errors.
In a later doubles play partnering with her sister Venus, the American pair lost to fourth seeded Russians Maria Kirilenko and Nadia Petrova 6-1, 6-4.
Hlavackova, a 2011 French Open doubles champion, had never been past the second round in singles at a major before this year.
Williams will next face Serbian Ana Ivanovic.
The 12th-seeded Serb beat Tsvetana Pironkova 6-0, 6-4. Ranked No.1 in the world in 2008, Ivanovic has struggled with injuries since then.
In men`s competition, top seed Roger Federer reached his 34th consecutive quarterfinal at a major after Mardy Fish withdrew for precautionary health reasons.
The World No.1 will next meet sixth-seeded Tomas Berdych, who beat 11th-seeded Nicolas Almagro 7-6 (4), 6-4, 6-1 in two hours.