NEW YORK -- When she was 12, doctors in her native China told Peng Shuai that she wouldn't be able to play tennis. She needed heart surgery to repair a defect, and for one long year she couldn't play.
"They say, because if I keep play, they worry about if I have a problem," Peng said.
On Tuesday, the unseeded Peng became the first woman into the US Open semifinals with a 6-2, 6-1 win over 17-year-old Belinda Bencic. At 28, she doesn't worry about her heart anymore, but in the hot and humid conditions on Arthur Ashe Stadium, Peng kept things brief. The match lasted just 64 minutes, ending when Bencic netted a backhand.
Now No. 39 in the rankings, Peng finds herself in the first Grand Slam semifinal of her career. She has beaten three seeds along the way, including No. 4 Agnieszka Radwanska and No. 14 Lucie Safarova -- and she hasn't dropped a set since she started her US Open bid. In fact, Peng hasn't been broken in her last 37 service games.
The semifinals of a Slam -- after her match, Peng could sit back in the interview chair at the USTA Billie Jean King National Tennis Center and smile at the moment.
"I dream about it," she said.
So how is she doing it? How can a woman who has been a contender on the WTA Tour but never ranked in the top 10 all of a sudden become unstoppable? Peng says that a succession of injuries have cleared up, allowing her to pursue that dream a little more directly.
"From the beginning year I was doing lot of fitness and also, like, I keep practice, try to improve my game," Peng said. "Maybe this time I find a way or I catch, like, right time."
Peng isn't even the best-known player from China. Li Na has won two majors, and Zheng Jie, who was Peng's first-round opponent, has reached two Grand Slam semifinals.
The Swiss Bencic, just 17, is coached by Martina Hingis' mother and former coach, Melanie Molitor. She has had a successful season given the limited tournaments she can play, a quarterfinal finish here and a third-round appearance at Wimbledon.
Bencic attributed some of the difficulty in playing Peng to the tricky angles honed in her doubles game, for which Peng is ranked third in the world.
"I think she has a dangerous game with both hands, and the ball is really coming different from her racket," Bencic said. "I had a little bit troubles with this today. Also angles are great. She's a great doubles player as well. It's good for her."
Peng said she wasn't so sure -- she still thinks the singles and doubles games are very different. But she does hit the angles, and she doesn't back off the baseline. Peng, when healthy, plays at a pace that can flummox opponents.
During Peng's match, but on another court, Serena Williams called a medical timeout and appeared to have her right foot and ankle tended to. Is the top-seeded player -- who has been on a roll here -- vulnerable? Williams plays her quarterfinal against No. 11 Flavia Pennetta on Wednesday. Williams is a potential final opponent if Peng can defeat the winner of the Caroline Wozniacki-Sara Errani quarterfinal.
But that will all work itself out. For now, Peng seemed happy to enjoy a career goal that she didn't know would come, and to look back at all the small steps that got her here.
"I think everybody, like, want to do their best in the Grand Slam ..." Peng said. "So now I am in the semis, I keep going dream."