NEW YORK -- Gael Monfils, a flashy Frenchman known more for his shot-making than results, beat Grigor Dimitrov 7-5, 7-6 (6), 7-5 on Tuesday to reach the quarterfinals of the U.S. Open for the first time since 2010.
The 20th-seeded Monfils pounded his chest and extended his arms after the seventh-seeded Dimitrov double-faulted on match point.
Monfils made two major quarterfinals in a season for the first time in his career. He also advanced that far at the French Open.
Dimitrov broke through to his first Grand Slam semifinal at Wimbledon but couldn't follow that up with another deep run.
In an entertaining match, both players made unbelievable gets, including Monfils' shot in the final game that he nearly curled around the net. Dimitrov got it back to win the point. But the match came down to break points: Monfils converted 3 of 4, Dimitrov just 1 of 7.
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.
Earlier, unseeded Peng Shuai of China beat 17-year-old Belinda Bencic 6-2, 6-1 to reach her first semifinal in 37 Grand Slam appearances.
Only five women have participated in more major tournaments 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.
The 58th-ranked Bencic was the youngest quarterfinalist at Flushing Meadows since her mentor, 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.
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.
In other men's matches with a spot in the final eight at stake, sixth-seeded Tomas Berdych meets Dominic Thiem, and No. 14-seeded Marin Cilic plays 26th-seeded Gilles Simon.
No. 1 Serena Williams, who faces 11th-seeded Flavia Pennetta in another quarterfinal Wednesday, lost in the doubles quarterfinals with 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 the first round of the main draw 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.