Venus Williams crashes out of China Open

World number one Angelique Kerber, meanwhile, continued her stellar season by beating qualifier Katerina Siniakova in two sets in her opening match in Beijing.

After a close first set, the former US Open semi-finalist Peng allowed the American veteran just one game point in the second to win 7-5, 6-1.

"In the first set I was really trying to fight because I think she got three set points," said Peng after the match.

"I think in the second set it's really important when I got the first three points. It gave me more motivation."

Peng, 30, came of age at the same time as China's first -- and only -- Grand Slam singles champion Li Na.

She reached a career high of 17 in 2011, the same year Li won her first Slam at Roland Garros and rose to world number five, taking with her the popularity of tennis in China.

But Peng's career has since been blighted by injury, which forced her to miss much of 2015 and pushed her to the brink of retirement.

"After the surgery, no one could guarantee I could come back to the court," Peng said.

"I'd like to take time to see if I can go further (in tennis)."

'Positive on court'

Czech Siniakova, 20, played an impressive net game against top seed Kerber but was unable to take control of the match, handing the German a 6-4, 6-4 win.

"She played really well, especially in the first set. I was trying to be patient and waiting for my shots and for my chances," said Kerber after the match.

The German won her second Grand Slam title of the year -- and her career -- at the US Open last month in the same week that also saw her rise to number one, dethroning long-reigning Serena Williams.

Kerber, 28, started the year ranked 10th but reached her first ever Grand Slam final at the Australian Open in January -- and scooped the crown.

Her strong run continued as she reached the final of Wimbledon and bagged an Olympic silver medal in Rio.

Kerber credits changing her on-court demeanour -- which once earned her the nickname "Dun Curr-ber" based on the internet meme for "don't care" -- for her late career renaissance.

"I think it came from a lot of experience... really focusing and trying to (be) more positive on court than negative," Kerber told reporters in Beijing.

"I think this is also one of the keys why I'm playing so good and so consistent, because it's really important to have your mind on the court."

Meanwhile, defending champion Garbine Muguruza booked her spot in the final 16, downing 21-year-old Yulia Putintseva in her second-round match.

The Spaniard has her eyes on making her second consecutive WTA Final -- the elite eight-player season finale -- and needs to reach the final in Beijing to guarantee her qualification this week.

On the men's side, David Ferrer and fellow Spaniard Roberto Bautista Agut both prevailed in their tougher-than-expected first-round matches.

Lucas Pouille ousted wildcard Lu Yen-Hsun of Taiwan in two sets -- and less than 50 minutes -- to take him a step closer to a rematch with Rafael Nadal.