Shenzhen, China (Sports Network) - Top seeds Li Na and Marion Bartoli were straight-set winners Wednesday in the second round of the inaugural Shenzhen Open.

The top-seeded Li battled through some trouble with her serve in a 6-3, 6-4 win over American Julia Cohen. The Chinese star had five double faults, but still managed to advance to a quarterfinal against eighth-seeded Bojana Jovanovski of Serbia.

Bartoli, this week's second seed, earned a 7-5, 6-4 victory over Swiss qualifier Stefanie Voegele. It was a bit more of a struggle for the Frenchwoman, who dropped just one game in her opening match against Hong Kong wild card Wing-Yau Chan and will next face fifth-seeded Czech Klara Zakopalova in the quarters.

China's Zhou Yi-Miao continued her run as lucky loser with a 4-6, 6-2, 7-6 (7-3) triumph over Taiwan's Kai-Chen Chang. Zhou made the main draw after replacing former world No. 1 Jelena Jankovic, who withdrew because of an illness.

Next up for Zhou will be Romanian veteran Monica Niculescu, while the other quarterfinal will feature Chinese sixth seed Peng Shuai against German Annika Beck.

This event serves as a tune-up for the Australian Open, which starts January 14.

The Sports Network