Andy Roddick walks off the court after retiring in his second-round match.
Serena Williams celebrates her 500th career win.
MELBOURNE, Australia (AP) -- Andy Roddick's attempt to win another Grand Slam title nearly a decade after his first ended Thursday at the Australian Open when he had to retire from his second-round match due to injury.
Former No. 1-ranked Roddick, whose only major win came at the 2003 US Open, was trailing Lleyton Hewitt 3-6, 6-3, 6-4 when he called the trainer to his courtside chair. He then walked over to Hewitt and shook the Australian player's hand, unable to continue after sustained what appeared to be a leg injury in the opening set.
Roddick had fallen to the court during the first set, but continued despite being in obvious pain.
Hewitt, who has won two major titles and was a finalist here in 2005, will play Canada's Milos Raonic in the third round.
Top-seeded Novak Djokovic advanced earlier Thursday, overcoming an early service break against Santiago Giraldo in a 6-3, 6-2, 6-1 victory at Melbourne Park.
A title this month would put him in select company. Only four players - Laver, Pete Sampras, Roger Federer and Rafael Nadal - have won three straight Grand Slam singles tournaments, and Djokovic could join them following his wins at last year's Wimbledon and US Open.
Second-seeded Nadal and third-seeded Federer, who are in the other half of the draw here, play back-to-back matches at Rod Laver Arena on Friday.
Fourth-seeded Andy Murray, who lost to Djokovic in the final here last year, also advanced Thursday, beating Edouard Roger-Vasselin of France 6-1, 6-4, 6-4. Murray is playing his first Grand Slam tournament since hiring eight-time major champion Ivan Lendl as his coach.
Earlier, five-time Australian Open champion Serena Williams notched her 500th career singles victory when she beat Barbora Zahlavova Strycova 6-0, 6-4 to advance to the third round. The left ankle she badly sprained two weeks ago wasn't an issue.
"It's totally fine. It was my good ankle, so I'm good,'' she said.
Williams won the Australian Open in 2009 and 2010, but didn't defend her title in 2011 because she was injured.
Her older sister, Venus, has a win-loss record of 589-147, but is missing the Australian Open to recover from illness.
Not quite. Martina Navratilova had a career record 1,442-219, and Chris Evert retired with a 1,309-146 win-loss mark.
With top-seeded Caroline Wozniacki having a day off, No. 2 Petra Kvitova moved into the third round with a 6-2, 2-6, 6-4 win over Carla Suarez Navarro. Kvitova, who lost in the first round at the US Open in the first major after winning Wimbledon, was down a service break in the third before recovering to beat the Spaniard.
Maria Sharapova, one of the three former champions in the women's draw, reached the third round after just two hours on court in two matches. The 2008 champion had a 6-0, 6-1 second-round win over U.S. qualifier Jamie Hampton in 64 minutes.
Sharapova did not play in any warmup events and spent nearly two weeks in Melbourne ahead of the season's first major while she rested an injured left ankle.
She'll meet No. 30 Angelique Kerber, who beat Canada's Stephanie Dubois 7-5, 6-1.
Seventh-seeded Vera Zvonareva, a two-time semifinalist at Melbourne Park, had a 6-1, 7-6 (3) over Lucie Hradecka. No. 21 Ana Ivanovic also advanced, beating Dutch player Michaella Krajicek 6-2, 6-3.
Ninth-seeded Marion Bartoli beat local hope and former quarterfinalist Jelena Dokic 6-3, 6-3 and No. 27 Maria Kirilenko of Russia topped Aleksandra Wozniak of Canada 6-4, 1-6, 6-2. Former U.S. Open champion Svetlana Kuznetsova beat American Sloane Stephens 7-6 (6), 7-5.
Three seeded players were beaten: No. 23 Roberta Vinci lost to China's Zheng Jie, No. 29 Nadia Petrova fell to Sara Errani and No. 25 Kaia Kanepi lost to Ekaterina Makarova.
No. 9 Janko Tipsarevic, No. 23 Milos Raonic of Canada, No. 24 Kei Nishikori of Japan and No. 27 Juan Ignacio Chela also progressed. Frenchman Michael Llodra beat No. 32 Alex Bogomolov Jr. 6-1, 6-3, 4-6, 5-7, 6-4 and Portugal's Frederico Gil beat No. 26 Marcel Granollers in four sets.
In a night match, No. 14 Gael Monfils beat Thomaz Bellucci of Brazil 2-6, 6-0, 6-4, 6-2 and will play Mikhail Kukushkin of Kazkakhstan in the third round. Kukushkin earlier beat No. 19 Viktor Troicki of Serbia 5-7, 6-4, 6-2, 4-6, 6-3.