FLUSHING MEADOWS, New York, Sept. 3 (Xinhua) -- Second seed Agnieszka Radwanska was shut out of US Open Monday with a 6-1, 6-4 loss to 20th seeded Italian Roberta Vinci.
Vinci, who had never been past the third round at a major tournament before Wimbledon this year, made a Grand Slam quarterfinal for the first time.
The victory gave the Italian a quarters showdown against her best friend and doubles parter Sara Errani, seeded 10th, who defeated Errani defeated Angelique Kerber 7-6 (5), 6-3.
The Italian duo, who won the title at Roland Garros this year, are still alive in doubles, reaching the quarterfinals as the No. 2 seeds.
"We are also very friends outside the court," Errani said of their success together. "This is one thing that helps very much on the court. But also because we are playing both very good. I think this year we are playing very good tennis."
Kerber advanced into the U.S. Open semifinals a year ago and had advanced to at least the quarters at the French Open and Wimbledon in 2012.
The sixth-seeded German double-faulted to end the first-set tiebreaker. She had 38 unforced errors.
Radwanska, coming off a runner-up finish at Wimbledon, was trying to become the first Polish woman to reach the quarterfinals at this tournament in the Open era. She had been 4-0 against Vinci prior to the encounter at Flushing Meadows.
Serena Williams didn't drop a game in advancing to the quarterfinals.
Williams beat 82nd-ranked Andrea Hlavackova 6-0, 6-0 in 57 minutes. It was the first time in 62 career victories at Flushing Meadows that the three-time U.S. 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 tournament before this year.
Williams will next face Ana Ivanovic, who is finally back in a Grand Slam quarterfinal more than four years after her French Open title.
The 12th-seeded Serb beat Tsvetana Pironkova 6-0, 6-4. Ranked No. 1 in the world in 2008, Ivanovic has struggled with injuries and her confidence since.
Top seed Roger Federer, in his 34th consecutive quarterfinal at a major tournament after Mardy Fish withdrew for precautionary health reasons, will meet sixth-seeded Tomas Berdych, who beat 11th-seeded Nicolas Almagro 7-6 (4), 6-4, 6-1 in two hours.