Pushing forward whenever possible, Roger Federer got back to the U.S. Open quarter-finals for the 10th time in 11 years with a 6-4, 6-3, 6-2 victory over 17th-seeded Roberto Bautista Agut of Spain on Tuesday night.

The one exception in that run of Flushing Meadows quarter-finals came in 2013, when Federer lost to Tommy Robredo in the fourth round. That was part of a stretch in which the 17-time Grand Slam title winner was bounced before the quarters three times in the span of four majors.

But things are different these days for the 33-year-old Federer. He's no longer bothered by a bad back. And he's no longer fiddling with trying to find the right racket, having settled on a new model with a larger head that he seems to be enjoying.

At Wimbledon in July, he got to his first Grand Slam final in two years, and even though he lost that match to Novak Djokovic, it signalled a real resurgence. On a windy evening against Bautista Agut, Federer moved well and won the point on 35 of 52 trips to the net.

"I'm happy I'm able to come forward now because … coming to net requires a lot of agility and explosivity and all that stuff, and I have it back," said Federer, a five-time champion at Flushing Meadows. "I'm happy I'm feeling good at net, too, because you've got to anticipate some and read some and it's working really well. So I hope I can keep it up."

Federer was broken only once, part of a three-game run for Bautista Agut that took the score from 5-1 to 5-4 in the first set. But Federer had no trouble the second time he tried to serve out that set, which he ended with a pair of aces.

In all, the second-seeded Federer needed less than two hours to improve to 25-1 in night matches at Arthur Ashe Stadium. This was Bautista Agut's first such occasion in the imposing, 23,771-capacity arena.

"Night session is very, very special here in New York," Federer said in an on-court interview.

Federer is 71-9 overall at the U.S. Open, tying Pete Sampras and Bill Tilden for the fifth-most match wins in tournament history behind Jimmy Connors' 98. Federer's .888 winning percentage is second behind the .910 of Tilden, who went 71-7 and won seven championships in the 1920s.

In Thursday's quarter-finals, Federer will play 20th-seeded Gael Monfils of France.

Unseeded Shuai reaches semis

Unseeded Peng Shuai of China beat 17-year-old Belinda Bencic 6-2, 6-1 in the U.S. Open on Tuesday to reach her first semifinal in 37 Grand Slam tournaments.

Only five women have participated in more majors before getting to a final four, and the relief brought the 28-year-old Peng to the brink of tears.

She said in her on-court interview that she at times thought about quitting the sport, but "my coach, my parents, they always tell me to try to keep going and never ever, give up."

The 39th-ranked Peng has not yet lost a set in the tournament. And she stayed consistent against Bencic, hitting 24 winners and committing only seven unforced errors. Her teenage opponent, meanwhile, appeared to become unglued in the muggy 91-degree heat of Arthur Ashe Stadium.

The 58th-ranked Bencic was the youngest quarter-finalist at Flushing Meadows since another Swiss girl, Martina Hingis, won the title at 16 in 1997. Bencic is coached by Hingis' mother, Melanie Molitor, and was issued a code violation for receiving help from her box while down 2-0 in the second set.

"It's 6-2, 2-0 and you're giving me a code violation?" Bencic yelled at the umpire. She went on to lose that game.

Unseeded semifinalists are rare. From 1977 to 1996, no unseeded women made it to the U.S. Open semifinals. Peng is now the sixth since the 2000 tournament.

Wozniacki upends No. 13 Errani

Caroline Wozniacki moved into her first Grand Slam semifinal in three years, overwhelming 13th-seeded Sara Errani of Italy 6-0, 6-1 Tuesday night in a wind-whipped match.

With the players' towels and fans' napkins and all sorts of things being tossed around by the stirred-up air, the 10th-seeded Wozniacki dealt with the conditions far better.

The match began competitively enough, with points lasting 22 and 23 strokes in the first game, and Errani earning four break points before 2009 U.S. Open runner-up Wozniacki eventually held.

Wozniacki wound up with a 26-12 edge in winners.

Denmark's Wozniacki, a former No. 1 who eliminated five-time major champion Maria Sharapova in the fourth round, will face unseeded Peng Shuai of China in the semifinals.

Serena's ankle a problem in doubles loss

Tenth-seeded Caroline Wozniacki, who eliminated five-time major champion Maria Sharapova in the fourth-round, takes on 13th-seeded Sara Errani in a night match for another semifinal spot.

Gael Monfils beat No. 7 Grigor Dmitrov 7-5, 7-6 (6), 7-5 to reach the quarter-finals for the first time since 2010.

The 20th-seeded Frenchman, who has always been known for his spectacular shots but inconsistent results, pounded his chest after the seventh-seeded Dmitrov hit a net cord and double-faulted on match point. Monfils reached the quarter-finals of the French Open this year. This victory gives him his second major quarter-finals appearance in the same season for first time.

Monfils moves on to play the winner of the night match between second-seeded Roger Federer and No. 17-seeded Roberto Bautista Agut of Spain.

The other quarter-final matchup on that half of the draw will be No. 14 Marin Cilic against No. 6 Tomas Berdych, who beat 20-year-old Dominic Thiem 6-1, 6-2, 6-4. Cilic edged No. 26 Gilles Simon, who was treated for a back problem early on, 5-7, 7-6 (3), 6-4, 3-6, 6-3.

Top-seeded and No. 1-ranked Serena Williams, who faces 11th-seeded Flavia Pennetta in another quarter-final Wednesday, lost in the doubles quarter-finals with her sister Venus. Serena had her right ankle re-taped during a medical timeout and later double-faulted on the last two points in a 7-6 (5), 6-4 loss to the fourth-seeded Russian duo of Ekaterina Makarova and Elena Vesnina.

And the run is over for U.S. Open darling CiCi Bellis. The 15-year-old Californian, who became an overnight sensation when she stunned 12th-seeded Dominika Cibulkova in Flushing Meadows' first round before losing in the second, lost her second-round juniors match to 17-year-old Russian Natalia Vikhlyantseva 7-6 (9), 2-6, 6-1.