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 semi-final 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 quarterfinalist at Flushing Meadows since another Swiss girl, Martina Hingis, won the title at 16 in 1997. Bencic is coached by Hingis's 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 semi-finals. Peng is now the sixth since the 2000 tournament.
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 semi-final spot.
Also in action later was second-seeded Roger Federer, who is seeking to get back to the U.S. Open quarterfinals after a surprising fourth-round exit last year. He plays No. 17-seeded Roberto Bautista Agut of Spain for the first time.
In other matches with a spot in the final eight at stake, sixth-seeded Tomas Berdych plays Dominic Thiem, seventh-seeded Grigor Dmitrov faces No. 20 Gael Monfils and No. 14-seeded Marin Cilic plays 26th-seeded Gilles Simon.
Top-seeded and No. 1-ranked Serena Williams, who faces 11th-seeded Flavia Pennetta in another quarterfinal 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.