Germany's Angelique Kerber beat Maria Sakkari of Greece 6-4, 6-4 to reach the Hong Kong Open second round on Tuesday as fourth seed Samantha Stosur suffered a shock loss to unseeded Japanese Nao Hibino.
World number one Kerber, who crashed out of last week's China Open in the round of 16 at the hands of Elina Svitolina, made five double faults but saved eight of 10 break points against world number 97 Sakkari.
"I had never played my opponent and that makes it tough," Kerber told reporters.
"It will be the same in my next match. But in the end I have to focus on my game."
The German will face American Louisa Chirico in the next round.
Fifth seed Caroline Wozniacki of Denmark beat China's Zheng Saisai 6-1, 6-4 to set up a second-round clash with Britain's Heather Watson who is seeded ninth and beat New Zealand's Marina Erakovic 7-5, 7-6(9).
Defending champion Jelena Jankovic of Serbia beat American Samantha Crawford 6-3, 6-1.
Stosur completed a hat-trick of first-round exits following her defeats at the China and Wuhan Opens as she was well beaten by Hibino who is ranked 84th in the world.
Image: Angelique Kerber hits a forehand
Photograph: Geoff Burke-USA TODAY Sports/via Reuters