Novak Djokovic beats Santiago Giraldo at 2012 Australian Open

Djokovic remains in contention to win a third successive Grand Slam title

Novak Djokovic continued his Australian Open title defence with a trouble-free win over Colombia's Santiago Giraldo.

The top seed overturned an early break before racing away to triumph 6-3 6-2 6-1 and set up a third-round meeting with Nicolas Mahut.

Jo-Wilfried Tsonga overcame Ricardo Mello 7-5 6-4 6-4, while Milos Raonic beat Philipp Petzschner in four sets.

Highly-rated Canadian Raonic will face Lleyton Hewitt who progressed after Andy Roddick retired hurt.

Roddick was two-sets-to-one down, trailing 3-6 6-3 6-4, when he called it a day following a leg injury, sustained while stretching to reach the ball when 2-0 behind in the second set.

The American had looked in fine form when he won the opening set, but needed medical treatment when trailing 3-0 in the second set and failed to recover, although he did battle on until Hewitt, surviving three break-back points, served out the third set.

There was also a victory for Janko Tipsarevic, who beat Australian wildcard James Duckworth 3-6 6-2 7-6 (7-5) 6-4.

The ninth seed will face Richard Gasquet in the third round after the Frenchman's opponent Andrey Golubev retired hurt when two sets down and trailing 3-0 in the third.

Djokovic, bidding to become only the fifth man in the Open era to win three consecutive Grand Slam singles tournaments, needed just one hour and 45 minutes to win his 16th match on the trot in a major tournament.

"You can't underestimate any opponent and Santiago is a tricky player," said the Serb, who broke the Colombian's serve seven times and always looked comfortable, hitting 27 winners during the match.

"It was really important to win the first set. I am trying to be physically fit and fresh for the upcoming rounds. The longer the tournament goes, the tougher it gets."

Elsewhere, fifth seed David Ferrer was tested but eventually beat Ryan Sweeting 6-7 (4-7) 6-2 3-6 6-2 6-3 and will play Juan Ignacio Chela, who beat Pablo Andujar 6-4 6-4 6-3.

France's Michael Llodra will face Andy Murray in the third round after completing a 6-1 6-3 4-6 5-7 6-4 victory over Alex Bogomolov, while Djokovic's next opponent Mahut beat Tatsuma Ito 1-6 7-6 (8-6) 6-2 6-2.

Llodra's compatriot and 14th seed Gael Monflis came from a set down to beat Thomaz Bellucci 2-6 6-0 6-4 6-2.

Monflis will next play Mikhail Kukushkin, who beat Viktor Troicki 5-7 6-4 6-2 4-6 6-3.

Meanwhile, the unseeded Frederico Gil defeated Marcel Granollers 3-6 6-4 4-6 3-6.

Gill must prepare to face 2008 finalist Tsonga, who admitted the Melbourne courts suited his game.

"The conditions here are good for me. The surface also, it's not really quick so maybe it's good for my game," said Tsonga.