Top-ranked Victoria Azarenka and No. 2 Maria Sharapova both reached the China Open quarter-finals Thursday with straight-set wins.

Azarenka easily beat Elena Vesnina of Russia 6-3, 6-3, while Sharapova defeated Slovenian qualifier Polona Hercog 6-0, 6-2 in Beijing.

Azarenka will next face Romina Oprandi of Switzerland, while Sharapova will play Angelique Kerber of Germany.

"I played really well in the beginning and got a little tense in the second set," Sharapova said. "But I felt like I really needed that challenge."

Sharapova won her first Grand Slam title in four years at the French Open.

Azarenka is hoping to rebound from last week in Tokyo when she withdrew from the tournament after a bout of dizziness in the third round. Azarenka has won four times this year, including the Australian Open.

Kerber beat former No. 1 Caroline Wozniacki of Denmark 6-1, 2-6, 6-4.

Li Na beat Shuai Peng 4-6, 6-2, 7-6 (3) in an all-Chinese clash, but Li's chances of becoming the first Chinese finalist in Beijing became harder as third-ranked Agnieszka Radwanska was next.

In men's singles, Mikhail Youzhny of Russia defeated Kevin Anderson of South Africa 6-3, 6-3 to make the Beijing quarter-finals for a fourth time.

Local wild card Zhang Ze upset fifth-seeded Richard Gasquet of France 6-4, 3-6, 6-4. Zhang, China's highest ranked player at 165th, has reached his first career quarterfinals. Gasquet won the Bangkok title last week.

Also winners were Feliciano Lopez of Spain and Sam Querrey of the U.S., who will meet on Friday.