Zheng Jie claimed a shock 6-3 6-7 (7-9) 6-4 win over Samantha Stosur to dump the home favourite out in the first round of the Apia International in Sydney.
Sixth seed Stosur, who also lost in the first round of the Brisbane International last week, slumped to defeat after a marathon contest which lasted two hours and 43 minutes.
Elsewhere, fourth seed Li Na battled into the second round after needing more than two hours record a 7-6 (7-2) 7-5 win over Christina McHale.
Former champion Li, who won the Shenzhen Open last week before travelling to Australia, was broken five times in a back-and-fourth match but eventually prevailed.
"It's very tough because in China it was like five or six degrees, but here it's over 30. And the jet lag - it was tough today. After finishing my match my legs felt like 200 kilos. I couldn't move," Li told the WTA Tour's official website.
"Yesterday my coach told me the most important match was today, because today it wasn't really about technique, it was about challenging my mind to show how strong I am on the court."
Li will next face Japanese qualifier Ayumi Morita, who defeated former world No 5 Daniela Hantuchova 1-6 6-3 6-3 in the first round.
Third seed Sara Errani eased through to the second round with a 6-1 6-3 win over Karolina Pliskova, while Errani's fellow Italian Roberta Vinci beat No 8 seed Nadia Petrova 7-5 7-5.
There was a shock win for 17-year-old American qualifier Madison Keys, who saw off world No 17 Lucie Safarova 6-2 6-1 in just 51 minutes.