NEW YORK — Roberta Vinci and Sara Errani planned to eat dinner together Monday and Tuesday, as usual.
Then on Wednesday, they'll try to slice and slam each other out of the U.S. Open.
"I'll be mean and so will she," Vinci said. "And then afterward, we'll be friends, just like before."
And one thing's for sure: An Italian woman will be in the semifinals.
The doubles partners each won a fourth-round singles match Monday in a straight-set upset, wearing identical pink and black outfits. The 29-year-old Vinci had never before reached a Grand Slam quarterfinal.
Since Francesca Schiavone became the first Italian woman to win a major title at the 2010 French Open, more firsts have been piling up for the country's players. Before this year, neither Vinci nor Errani had made it past the third round at a major tournament. Then Errani got to the quarters at the Australian Open — and topped that with a runner-up finish at Roland Garros.
Vinci advanced to the fourth round for the first time at Wimbledon. On Monday, she knocked off second-seeded Agnieszka Radwanska 6-1, 6-4. Vinci ran to her box to celebrate after breaking the Pole's serve to end the match, tears in her eyes.
"Tears, certainly, of joy, of nerves, of fear at the end," she said. "All beautiful — actually, really beautiful — emotions."
The 10th-seeded Errani defeated Angelique Kerber 7-6 (5), 6-3. She and Vinci are still alive in doubles, in the quarterfinals as the No. 2 seed. They won the French Open title this year.
Their friendship certainly benefits their partnership on the court, Errani said.
"But also because we are playing both very good," she said. "I think this year we are playing very good tennis."
The two don't warm up together before singles matches, so in that sense Wednesday won't feel strange. Vinci and Errani have faced each other five times — with Vinci winning the first two and Errani the last three.
"It definitely won't be an easy match from a mental perspective," Vinci said. "We know each other well. We practice together often. We play doubles together. We know everything about each other."
Kerber made a surprise run to 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, who had 38 unforced errors, double-faulted to end the first-set tiebreaker.
When Kerber's final forehand bounced off the net cord and back, Errani dropped her racket and pumped both fists.
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 the 20th-seeded Vinci.
"She's really playing much better this year than before," Radwanska said. "Really had some good results this year."
Even with that success, Vinci couldn't have envisioned this run when she looked at her draw here. She beat 13th-seeded Dominika Cibulkova in the third round.
"I definitely didn't think, 'Oh, I'll make it to the quarters,'" she said. "No way."
AP Tennis Writer Howard Fendrich contributed to this report.
Follow Rachel Cohen at https://twitter.com/rachelcohenap