NEW YORK -- Unseeded Peng Shuai of China beat 17-year-old Belinda Bencic 6-2, 6-1 in the US 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."
Peng will next face Caroline Wozniacki, who reached her first Grand Slam semifinal in three years by overwhelming 13th-seeded Sara Errani of Italy 6-0, 6-1 in a wind-whipped night match.
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' 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 US Open semifinals. Peng is now the sixth since the 2000 tournament.
Wozniacki had not been to the semis at any major tournament since losing at that stage at Flushing Meadows in 2011.
With the players' towels and spectators' napkins and all sorts of things being tossed around by the stirred-up air, the 10th-seeded Wozniacki dealt with the conditions far better than Errani. Although not right away.
The match began competitively enough, with a pair of points that lasted more than 20 strokes apiece in the first game. Errani -- who defeated Venus Williams in the third round -- earned four break points before 2009 US Open runner-up Wozniacki eventually held despite a double-fault in which one serve didn't come close to reaching the net.
Winning that opening game "was very important," Wozniacki said. "You always go out there and (can be) a little bit nervous. ... The second serve landed by my feet, and I kind of knew it was going to be tricky with the wind.''
She turned out to be just fine, ending up with a 26-12 edge in winners. Wozniacki also won 26 of 34 points served by Errani, the runner-up at the 2012 French Open and a semifinalist in New York that year.
Wozniacki had not been to the semis at any major tournament since losing at that stage at Flushing Meadows in 2011.
"It means so much to me,'' Denmark's Wozniacki said in an on-court interview. "It's been a pretty up-and-down year for me, and to be here in the semifinals of the US Open once again is just an incredible feeling. Definitely, hard work pays off.''
Top-seeded and No. 1-ranked Serena Williams, who faces 11th-seeded Flavia Pennetta in another quarterfinal Wednesday, lost in the doubles quarterfinals 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 US 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.
Information from The Associated Press was used in this report.