Novak Djokovic of Serbia watches a return during a practice session ahead of the Australian Open in Melbourne on Wednesday. Photo: AFP

Novak Djokovic is hitting ever greater heights ahead of the Australian Open - posing problems for his rivals, and raising distant hopes of the first-ever men's "Golden Slam."

Picking up where he left off after a blistering 2015, the world No.1 destroyed Rafa Nadal in last week's Qatar Open final, in a performance the Spaniard called "stratospheric."

"I played against a player who did everything perfect. I know nobody playing tennis like this ever," said Nadal, who has won 14 Grand Slam titles.

No male player, and only Steffi Graf on the women's side, has ever achieved the "Golden Slam": winning all four major titles and Olympic singles gold in a single year.

Last season Djokovic fell just one victory short of the first calendar year Grand Slam since Rod Laver in 1969, after losing the French Open final to Stan Wawrinka.

Acknowledging his form, the 28-year-old said in Doha, "I'm hoping that I can actually peak and play as well as I did today in Melbourne."

A strong performance looks likely in Melbourne, Djokovic's most successful Grand Slam where he has won five out of five finals, including last year against Andy Murray.

But the 10-time major champion will not be looking too far beyond the year's opening Grand Slam, which starts Monday.

"My thoughts are only directed to Melbourne and what I need to do there," he said.

'It's a huge challenge'

Murray, who will be in the bottom half of the men's draw and seeded to face Djokovic in the January 31 final, sees the Serb as a huge challenge.

"What Novak is doing ... last year he had an incredible year," he said. "Final of every tournament bar one.

"It's been tough playing in an era with Novak, Roger [Federer] and Rafa [Nadal] but at the same time to have guys like that to always be trying to catch up to, to have to improve to try and beat them, it's a huge challenge."

Murray carries the baggage of losing four Melbourne finals - three of them to Djokovic - but is continuing his dogged pursuit of a breakthrough.

"I'm doing everything I can to try and win here," said the 28-year-old Scot, who has promised to leave early if his wife Kim Sears gives birth.

"My No.1 goal is to try and win here. It'd mean a lot because of how many times I've been close."

Classic final

Federer, as the third seed on rankings, could face either Djokovic or Murray in the semifinals as the 17-time Grand Slam champion looks to win his first major title since Wimbledon in 2012.

The Swiss maestro has won four Australian Opens, but lost to Djokovic at last year's Wimbledon and US Open finals. At 34, he is running out of time to add to his all-time record haul of Grand Slam titles.

"Of course, Novak is the favorite for the ­Australian Open. Plus he's played well there ­historically," Federer said last week.

Nadal has won once in Australia, over Federer in a classic five-set final in 2009, and has had some of his career low points with tournament-ending injuries in Melbourne.

But he maintains he can do well as he pursues his comeback from a disappointing 2015, when he failed to any Grand Slam titles.

"I am playing well, and I'm gonna keep working hard to try to be ready for Australia. And I think I will be. I am motivated for it," the Spanish left-hander said.

Switzerland's Wawrinka will also be a contender after he conquered Djokovic on the way to winning the 2014 Australian Open, and beat him again in last year's French Open final.

The world No.4 tuned up by beating Croatia's Borna Coric for a third straight Chennai Open title in India last week.

Outside the top five, Japan's world No.7 Kei Nishikori will be looking to get past the quarters for the first time in Melbourne.

Meanwhile, local interest will focus on the antics of talented but wayward young Aussies Bernard Tomic and Nick Kyrgios.