(CNN) -

China's population may be in excess of 1.3 billion inhabitants but only two of its players had ever reached a grand slam semifinal -- until Tuesday.

That was when unseeded Peng Shuai put years of frustration, thoughts of retirement and major heart surgery to one side as she blew away Swiss teen Belinda Bencic at the U.S. Open.

At her 37th grand slam, the 28-year-old was finally into her first semifinals.

The buildup had mainly focused on the 17-year-old Bencic but it was the little known Peng -- far more recognized as a doubles player -- who stole the show with a powerful display.

By so doing, she follows in the footsteps of Li Na, a two-time grand slam winner, and Zheng Jie, who reached semifinals at Wimbledon (2008) and the Australian Open (2010).

"It's a little bit too exciting," Peng said on court after her 6-2 6-1 victory, earning a round of applause after pausing as emotion got the better of her.

"I love tennis, I love to play."

That much is clear from her back story.

Aged 12, Peng went against her family wishes to undergo a major operation to repair a fault in her heart.

The procedure was so complicated surgeons had to access her heart through her left leg but as Peng made clear in a 2008 advertisement, there was one fundamental reason she went through with it.

"All I thought was very simple: if I want to continue tennis, I need to have this operation," she said in the Adidas advert.

Nearly two decades later, her tenacity was rewarded when she achieved the No. 1 ranking in doubles.

By so doing, she became the first Chinese to ever achieve top spot -- whether in singles or doubles, male or female.

Despite the ranking, a player who has never won a singles title revealed she had been wracked by doubts in recent times.

"A career is tough sometimes," said Peng in victory. "I've thought about giving up, stopping playing (singles), because I didn't know if I can make it, but my coach and parents told me to never give up."

With her two-fisted ground strokes proving too much for a rattled Bencic, the youngest U.S. Open quarterfinalist since 1997, Peng hit 24 winners.

Although Zheng was the first Chinese player to reach a grand slam semifinal, world No. 3 Li has taken the country's tennis further.

She won its first singles grand slam at the 2011 French Open, before clinching a second title at this year's Australian Open.

No Chinese woman has ever reached the U.S. Open singles final, a record that Peng -- who has won two grand slam doubles titles in the last year -- will try to correct on Thursday.

She will meet 2009 finalist Caroline Wozniacki, who continued her career resurgence by crushing Italian 13th seed Sara Errani 6-0 6-1 later Tuesday.

The former world No. 1, who has a 5-1 career record over Peng, reached the last four of a grand slam for the first time since 2011, also in New York.

"She was much stronger than me physically tonight," said Errani, a semifinalist in 2012. "She doesn't let you play. She never misses.

"And every point was a long point, and it made me feel worse, physically."

Serena Williams is in action on Wednesday against Italy's Flavia Pennetta, but she suffered a frustrating day on Tuesday.

Not only did she lose her doubles quarterfinal with sister Venus to Russian pair Ekaterina Makarova and Elena Vesnina, but she also suffered an injury scare.

The world No. 1's right foot had to be heavily bandaged early in the second set of the 7-6 6-4 defeat.

In the men's event, second seed Roger Federer marched into the quarterfinals for the 10th time in the last 11 years with an aggressive 6-4 6-3 6-2 win over Spanish 17th seed Roberto Bautista Agut.

The five-time U.S. champion, seeking his first final appearance since losing the 2009 title match, came to the net 50 times as he comfortably set up a clash with French 20th seed Gael Monfils.

"I'm happy I'm able to come forward now because coming to net requires a lot of agility and explosiveness, and I have it back," said the veteran 17-time grand slam winner.

He has a 7-2 record over Monfils, beating him in three sets on the way to winning the Cincinnati title last month.

"I know exactly how I need to play him," Federer said. "I know I'll be coming in; he knows he'll be defending. He'll be wanting to serve well and play big as well."

Monfils, known for his all-action style, was in impressive form as he overcame a sluggish Grigor Dimitrov 7-5 7-6 (8-6) 7-5 to reach the quarterfinals at Flushing Meadows for a third time.

Sixth seed Tomas Berdych will play Croatia's Marin Cilic in the quarterfinals, after the Czech beat Austria's Dominic Thiem 6-1 6-2 6-4.

Cilic, seeded 14th, came from behind to beat Richard Gasquet 5-7 7-6 (7-3) 6-4 3-6 6-3, avenging his five-set defeat by the Frenchman at January's Australian Open.

In Wednesday's opening quarterfinals, Australian Open champion Stanislas Wawrinka takes on Japanese 10th seed Kei Nishikori, then in the late session world No. 1 Novak Djokovic plays Andy Murray in a repeat of the 2012 title match.