Novak Djokovic of Serbia celebrates after defeating Florian Mayer of Germany in their men's singles tennis match at the Wimbledon Tennis Championships, in London June 25, 2013. [Photo/Agencies]

LONDON -- Top seeds Novak Djokovic and Serena Williams advanced to the second round at the Wimbledon Championships here on Tuesday while three Chinese women players had mixed fortunes.

World No. 1 Djokovic, the 2011 champion, defeated Germany's Florian Mayer 6-3, 7-5, 6-4 in their fourth meeting, which also proved his fourth loss.

"Of course I'm very pleased," said the Serb. "This was my first match back at the biggest tournament in sport, and it was a very satisfying performance. You cannot take anything or anyone for granted."

Women's defending champion Williams, bidding for her sixth Wimbledon title and 17th Grand Slam win, beat Luxembourg's Mandy Minella 6-1, 6-3.

"I feel that I'm always ready," the champion said. "You know, I never feel invincible. I always feel that I have to be ready for each opponent in each game, and I never become overconfident. I think when I do or if I do, that's the moment that I'm most vulnerable."

China's number one player Li Na, who was out at the second round at the French Open, breezed past Dutchwoman Michaella Krajicek 6-1, 6-1.

The 31-year-old former French Open champion said, "It was a pretty good start to Wimbledon. Because the last two years I did not do well on the grass. I have to get used to playing on the grass. I was feeling pretty happy."

Li's compatriot Peng Shuai, the 24-year-old, braved a knee injury to beat Spain's Anabel Medina Garrigues 6-3, 6-2.

But another Chinese player, Zheng Jie, a semifinalist in 2008, suffered a surprise defeat to 20-year-old Caroline Garcia of France 6-3, 6-4.

Zheng, 30, has sustained a leg injury while playing at the Chinese National Games after the French Open.

"I failed to play any warmup matches after the French Open," she said. "Changing the surfaces within one month from clay to hard court and then to grass, it is very easy to be injured."

Fourth seed David Ferrer of Spain survived a scare to defeat 101-ranked Martin Alund of Argentina 6-1, 4-6, 7-5, 6-2 in two hours nine minutes.

Russia's Maria Kirilenko, last year's quarterfinalist, surrendered a defeat to Britain's world number 38, Laura Robson 6- 3, 6-4. Her compatriot and 21st seeded Anastasia Pavlyuchenkova also slumped to a 6-0, 6-1 loss to Bulgaria's Tsvetana Pironkova.

Another Russian 13th seed Nadia Petrova went out 6-3, 6-2 to Karolina Pliskova of the Czech Republic.

Polish fourth seed Agnieszka Radwanska enjoyed a 6-1, 6-1 win over Austrian qualifier Yvonne Meusberger.