CHINESE doubles specialist Peng Shuai supplied a shocking start to the second round of the US Open by upsetting fourth-seeded Poland's Agnieszka Radwanska 6-3 6-4 at a hot, humid Flushing Meadows.
The doubles world number one used piercing, two-fisted ground strokes to put Radwanska on the defensive and claimed the biggest scalp of the tournament so far on her third match point with a backhand crosscourt winner that brushed the corner lines.
Radwanska, winner in the Montreal hardcourt run-up to the US Open and a semi-finalist at this year's Australian Open, saved a match point in the ninth game to hold serve for 5-4 and fended off another in the next game before Peng's last winner.
The 28-year-old Peng, the French Open doubles champion and 2013 Wimbledon doubles winner who is seeking her first career WTA Tour singles title, registered 28 winners in the 96-minute match at Louis Armstrong Stadium.
"I had two match points and didn't make it," Peng said in an on court interview about two backhand errors that prolonged the match.
"But I just said 'fight, fight' and it's an amazing time for me," added Peng, who has 16 career doubles wins and in February became the first Chinese player to become a world number one in tennis.
The Chinese, who entered the contest 3-22 lifetime against top-five opponents, was masterful in turning points of the match. Peng won three of five break points against Radwanska, who succeeded only once in seven opportunities to break.
She has six career singles runner-up finishes, including this year in Shenzhen, and will be aiming to improve on her best grand slam singles result, having reached the fourth round four times, including at this year's Wimbledon.
"I still have a lot to learn," Peng said.
"I will try to keep on fighting. I still have to working hard, keep going and fighting and improve my tennis."
Peng, ranked 39th in singles, will play 28th seed Roberta Vinci in third round. The Italian advanced with a 2-6 6-4 6-1 win against Irina-Camelia Begu of Romania.
Johanna Larsson of Sweden eliminated another seed with an impressive threeset 5-7 6-4 6-2 upset of 21st-seeded American Sloane Stephens, a 2013 Australian Open semi-finalist.