MELBOURNE: Defending champion Rafael Nadal says this year's Australian Open is a lottery, with any one of a dozen players capable of winning.

The world number two Spaniard, who beat Roger Federer here last year in a gripping five-set final, admitted he was not the favourite this time after his injury layoff, but didn't want to say who he thought was.

"We will see what happens, I don't know," he said.

"A lot of players can win right now. I don't want to say everybody, but like 12 players, 13 players have a good chance."

Federer is obviously one of them, as is Nadal, Andy Murray and Novak Djokovic, with Nikolay Davydenko the form player having beaten the Spaniard in the Qatar Open final this month.

Nadal's failure to win that tournament means he comes into the opening Grand Slam of the season without a title in eight months, with the last one coming on the Barcelona clay in April.

Nadal said he hadn't had bad results, but was just struggling to get back to winning tournaments.

"I didn't have bad results the last five months, but I didn't have perfect results," he said.

"But I played, I was there (for) all the tournaments. Sure, it's true, playing against the top players I didn't have very good results, but I wasn't playing bad. I just need a little bit more."

With injuries hampering the 23-year-old for much of last year, he faces a telling time at the Australian Open, which should provide a guide as to his current standing in men's tennis.

He insists the confidence is there, it's just a question of once again winning a final.

"The confidence? The only way to have confidence is winning matches, winning important matches. I did that in Abu Dhabi and I did that in Doha," he said, referring to his two warm-up tournaments.

"So I think I am in the right way. It needs a little bit more time ... but I am ready to try to play my best tennis. I think I am playing well, I think I am playing much better than what I did in the last four months."

He opens his tournament with a first round match against Australian Peter Luczak, with Briton Andy Murray looming as a possible quarter-final opponent.

Nadal was not ready to look that far ahead.

"I never talk about quarter-finals before getting there," he said. "There are four matches until the quarter-finals. We will see what's happen before that."