Roberta Vinci of Italy celebrates after defeating Agnieszka Radwanska of Poland in their women's singles match at the US Open tennis tournament in New York September 3, 2012.  [Photo/Agencies]

NEW YORK - Roberta Vinci toppled second seed Agnieszka Radwanska to cap a rousing upset double for Italy at the US Open on Monday that also put her doubles partner Sara Errani into the women's singles quarter-finals.

Errani, the 10th seed, beat sixth-seeded Angelique Kerber of Germany 7-6 6-3, and 20th seed Vinci followed onto Louis Armstrong Stadium court for a 6-1 6-4 shocker to end a doubly delightful afternoon for Italian fans at Flushing Meadows.

The victories put the Italian pair, who are seeded second and already into the quarter-finals of the doubles competition, into the singles quarter-finals against one another, but that was further cause for celebration, according to Vinci.

"I'm happy to play against her, for sure an Italian goes to the semi-final," said 29-year-old Vinci after improving on her fourth-round advance at this year's Wimbledon championship that had marked her best grand slam result.

"She's my best friend, so I'm very happy to play against her, for sure."

Vinci said she was overjoyed to join the recent rise of Italian women's players.

"For sure, for sure. When (Francesca) Schiavone won Roland Garros (2010) and Flavia (Pennetta) goes to top 10, also Sara in the final in Roland Garros," Vinci said, rattling off accomplishments by her compatriots.

"Me, I try to come like the other ones for sure."

'Incredible Fight'

Vinci had lost all four of her previous matches against Radwanska, but she had her Polish opponent off balance in their Round of 16 clash.

Vinci outplayed Radwanska with 29 winners, and made just one unforced error from the backhand side.

"She's really playing very uncomfortable tennis to play," said Radwanska, who reached her first grand slam final this summer at Wimbledon, falling to Serena Williams.

"She really mixes it up. A lot of slice, then suddenly hitting very well from the forehand side, then kick serve, dropshots, volleys as well, coming to the net."

Vinci said her variety can bother opponents.

"I mix a lot of balls. I go to the net. I play a lot of slice, so it's different," said Vinci. "Probably she doesn't like my slice. Also when I go to the net, probably her passing is not so good. That's why I won today probably."

Errani, who fell in the French Open final this season to Maria Sharapova, had a tougher time against Kerber, who battled the Italian through a 71-minute opening set before losing 7-5 in a tiebreaker.

The Italian needed nearly two hours to prevail against a chance-taking rival who hit 13 more winners but made 17 more unforced errors.

"It was incredible fight," said Errani. "It was a very difficult match mentally and also physically. It was just a matter of a few points."