BEIJING — Two-time champion Novak Djokovic reached the China Open quarterfinals after dismissing Carlos Berlocq of Argentina 6-1, 6-3 on Wednesday.
Djokovic rushed through the first set then lost his serve twice in the second before winning the second-round match.
The Serb, champion in 2009 and 2010 in his only previous appearances in Beijing, faces Jurgen Melzer on Friday after the Austrian defeated Alexandr Dolgopolov 7-6 (9), 2-6, 6-1.
Florian Mayer of Germany also made the last eight.
Women's defending champion Agnieszka Radwanska needed more than two hours to put away Spanish qualifier Lourdes Dominguez Lino of Spain 2-6, 6-1, 6-4.
Radwanska, coming off a loss in the final of the Japan Open on Sunday, struggled in her first matchup against the Spaniard. Radwanska broke six times and lost her own serve seven times.
Second-ranked Maria Sharapova downed Sorana Cirstea of Romania 6-2, 6-2, and Slovenian qualifier Polana Hercog rallied from 5-1 down in the third set to beat Ekaterina Makarova 7-6 (5), 3-6, 7-6 (3).
Ana Ivanovic and Jelena Jankovic were knocked out of the third round in straight sets.
Ivanovic was ousted 6-4, 6-3 by Romina Oprandi of Switzerland, who replaced an ill Serena Williams in the draw.
Jankovic fell apart after leading 5-2, going out to Carla Suarez Navarro of Spain 7-5, 6-4.
At Tokyo, defending champion Andy Murray advanced to the quarterfinals of the Japan Open by beating Lukas Lacko of Slovakia 6-1, 6-2.
The third-ranked Murray lost only two points in the first five games and even threw in a few drop shots in a match that was completed with the roof Ariake Colosseum closed because of rain.
The U.S. Open champion and Olympic gold medalist broke Lacko in the third and seventh games of the second set and closed out the match on serve.
Seventh-seeded Stanislas Wawrinka of Switzerland also advanced to the quarterfinals, beating Jeremy Chardy of France 7-6 (1), 6-7 (6), 7-5. Chardy saved three match points in the second-set tiebreaker, but was broken in the 11th game of the final set.
Also, third-seeded Janko Tipsarevic of Serbia rallied to beat Gilles Simon of France 4-6, 6-3, 6-1 in the first round, and fourth-seeded Juan Monaco of Argentina defeated Bulgarian qualifier Grigor Dimitrov 6-2, 6-1.
Tipsarevic, ranked ninth in the world, was broken twice in the opening set but bounced back to eliminate the unseeded Simon.