Beijing - An out of sorts world number two Novak Djokovic extended his unbeaten record at the China Open in Beijing on Tuesday, requiring three sets to defeat qualifier Michael Berrer of Germany.
The Serbian, playing his first match since losing to Andy Murray in the US Open final last month, progressed to the second round with a 6-1, 6-7 (3/7), 6-2 victory, however it was a performance that was far from impressive.
Djokovic, 25, took the first set with ease but lost the second on a tie break after hitting several unforced errors against the left-hander, ranked 123rd in the ATP standings, before improving his groundstrokes for the third.
The number one seed has won China's Open on the two occasions he has entered, in 2009 and 2010, but missed last year because of injury.
Elsewhere, third seed Jo-Wilfried Tsonga of France battled to a three-set victory over Uzbekistan's unseeded Denis Istomin.
The world number seven lost the first set but came back to win 4-6, 6-1, 7-6 (7/3).
Tsonga's countryman Julien Benneteau, who lost in the final of the Malaysian Open just two days ago, was forced to retire shortly into the second set, handing Italy's Andreas Seppi the easiest of routes to the second round.
In the women's event, Chinese star Li Na brushed aside on-form Nadia Petrova of Russia in straight sets to progress to the last 16.
Asia's top women's player, who needs a strong showing this week to qualify for the WTA Championships in Istanbul later this month, won the match convincingly at a packed National Tennis Stadium 6-1, 6-2.
It was the 2011 French Open champion's first win against Petrova, who triumphed at the Pan Pacific Open in Tokyo on Saturday, in seven attempts.
"That's the charm in playing tennis. Every day you can challenge yourself," Li said.
"You are defeated consecutively, but it doesn't mean you are defeated by her all the time. This is sport. You never know what's going to happen.
"I'm very much glad to see that I'm still making progress in this match," she added.
Thirty-year-old Li, who has never won her home tournament, played at a frenetic pace throughout, breaking her opponent's serve twice in the first set and three times in the second.
Li was broken just once - in the sixth game of the second set, which lasted more than 13 minutes - and served consistently better than Petrova, hitting five aces to her opponent's one.
Li, ranked eighth in the world and seeded seventh in Beijing, will play compatriot Peng Shuai in the third round of the tournament - the fourth and final compulsory event of the women's calendar.
Asia's only Grand Slam winner is in eighth position in the race to compete at the $4.9-million end-of-season Championships, featuring the year's top eight players, two places ahead of France's Marion Bartoli.
Bartoli, the China Open's ninth seed, also progressed Tuesday, defeating Ayumi Morita of Japan 6-4, 6-3 while Spain's Lourdes Dominguez Lino knocked out Britain's Laura Robson 7-5, 6-3.
Fifth seed Angelique Kerber of Germany beat Lara Arruabarrena-Vecino of Spain 6-2, 6-0, while defending champion Agnieszka Radwanska also went through, defeating China's Zhang Shuai 6-2, 6-3.
Results on Tuesday at the China Open, an ATP-WTA tournament on outdoor hard-courts at The Beijing Tennis Centre (seedings in parentheses):
Novak Djokovic (1), Serbia, def. Michael Berrer, Germany, 6-1, 6-7 (3/7), 6-2.
Nikolay Davydenko, Russia, def. Alex Bogomolov Jr., Russia, 7-5, 6-1.
Jo-Wilfried Tsonga (3), France, def. Denis Istomin, Uzbekistan, 4-6, 6-1, 7-6 (7/3).
Mikhail Youzhny, Russia, def. Tommy Haas (7), Germany, 6-4, 4-6, 6-2.
Jurgen Melzer, Austria, def. Pablo Andujar, Spain, 6-1, 4-6, 7-6 (7/3).
Andreas Seppi, Italy, def. Julien Benneteau, France, 6-1, 2-0, retired.
Richard Gasquet (5), France, def. Matthew Ebden, Australia, 6-2, 6-4.
Feliciano Lopez, Spain, def. Ryan Harrison, United States, 7-6 (7/3), 5-7, 6-2.
Yen-hsun Lu, Taiwan, def. David Ferrer (2), Spain, 5-4, retired.
Li Na (7), China, def. Nadia Petrova, Russia, 6-1, 6-2.
Marion Bartoli (9), France, def. Ayumi Morita, Japan, 6-4, 6-3.
Jelena Jankovic, Serbia, def. Monica Niculescu, Romania, 6-2, 6-1.
Romina Oprandi, Switzerland, def. Camila Giorgi, Italy, 7-5, 6-2.
Lourdes Dominguez Lino, Spain, def. Laura Robson, Britain, 7-5, 6-3.
Agnieszka Radwanska (3), Poland, def. Zhang Shuai, China, 6-2, 6-3.
Angelique Kerber (5), Germany, def. Lara Arruabarrena-Vecino, Spain, 6-2, 6-0.
Caroline Wozniacki (10), Denmark, def. Su-wei Hsieh, Taiwan, 6-7 (5/7), 7-6 (7/3), 6-0.
Julia Goerges, Germany, def. Sam Stosur (8), Australia, 7-6 (7/2), 4-6, 7-5.
Victoria Azarenka (1), Belarus, def. Sabine Lisicki, Germany, 6-4, 6-2.