Djokovic is the one to beat

Novak Djokovic bids for an unprecedented third straight Australian Open title from today, with Andy Murray and Roger Federer shaping up as his biggest challengers.

Argentina's Juan Martin del Potro is the only man besides Djokovic, Rafal Nadal, Federer and Murray to win a Grand Slam tournament since 2005, but the Serb said there were many who could threaten their dominance.

"It's probably expected that the three of us, and Nadal, of course, would still be the main candidates to win all the major titles," Djokovic said.

"But I wouldn't underestimate Del Potro, [Jo-Wilfried] Tsonga, [David] Ferrer, [Tomas] Berdych . anybody who is in the top 10.

"I'm sure there's a bunch of new young players coming up like [Bernard] Tomic, [Grigor] Dimitrov, and [Milos] Raonic.

"I don't think it's nice for me to predict that we three will be champions of all Grand Slams this year."

But the odds favour Djokovic, who is targeting a third straight Australian title, a feat that has not been achieved in the professional era.

Nadal is not playing because of injury, robbing Melbourne Park of a repeat of last year's epic final when Djokovic finally tamed the Spaniard at 1.40am after a final that lasted a record five hours and 53 minutes - and left him with bleeding toes.

But Djokovic will face a stiff challenge from the newly assertive Murray, fresh from his first Grand Slam win and keen to avenge his final and semifinal defeats to Djokovic in Melbourne in 2011 and last year.

Also pressing hard will be Federer, holder of an unmatched 17 Grand Slams and hungry for more, even though, at 31, he is conceding six years to his rivals.

Murray, 25, said last year's Grand Slam breakthrough at Flushing Meadows eased the pressure and set him up perfectly to build on the best year of his career.

Murray, the world No3, was thrashed by Djokovic in the 2011 Australian Open decider, and narrowly lost out in their thrilling five-set semifinal last year.

But the Scot then beat Djokovic on his way to London Olympics gold, and again in the US Open final as he became Britain's first male Grand Slam singles winner since Fred Perry in 1936.

On the women's side , Serena Williams goes into the tournament as red-hot favourite.

She is going for a sixth title with even world No1 Victoria Azarenka admitting that the American is the player to beat.

Williams starts her 13th Melbourne campaign tomorrow against Romania's Edina Gallovits-Hall, fresh from claiming her 47th career title in Brisbane.