OSAKA, Japan - All three seeded players in second round action Thursday at the relatively upset-free HP Open got through in straight sets, but it was not smooth sailing for one of them.

Six of the original eight seeds will compete in Friday's quarterfinals, however, No.6 seed Aleksandra Wozniak was given all she could handle by 18-year-old qualifier Chang Kai-Chen, eventually prevailing, 75 76(2). The Canadian won four straight games to take the first set after being down 5-3. In the second set, she was up 5-1 before losing five straight games, then regained her composure and held serve to force the tie-break, where she cruised to victory.

Wozniak, whose year has been highlighted by a runner-up showing in Ponte Vedra Beach and semifinal appearances in Eastbourne and Québec City, will next play the woman who routed her in that final in Florida - Caroline Wozniacki. The No.1 seed had an easy time Thursday with Katie O'Brien, 60 61. The Dane's quarterfinal with Wozniak should be an intriguing one, as they have already played four times this year and five overall, with two of the matches having been extended to three sets. Wozniacki holds a 4-1 edge in the series, but Wozniak recorded her lone win in their most recent meeting two weeks ago in Tokyo.

Also Thursday, third-seeded Samantha Stosur handled Akiko Morigami, 61 62, and Jill Craybas got past Mathilde Johansson, 26 62 60, to set up a clash, which will be Craybas' first quarterfinal of the year. In the quarters on the bottom half of the draw, fourth-seeded Francesca Schiavone will play seventh-seeded Melinda Czink and second-seeded Marion Bartoli will take on Sania Mirza.