MELBOURNE (Reuters) - Novak Djokovic spent 2015 relentlessly trampling on the hopes and dreams of would-be challengers and the world number one again looms as the reality check to their new season ambitions when the Australian Open gets underway on Monday.

Serbia's Novak Djokovic (L) talks with Switzerland's Stan Wawrinka as they take a break during a practice session at Melbourne Park, Australia, January 14, 2016. The Australian Open tennis tournament starts January 18. REUTERS/David Gray

The defending champion will start as raging favourite for a sixth title at the year’s first grand slam, continuing the domination of men’s tennis that saw the Serb win 11 titles last year and three of the four majors.

Beating the red-hot world number one is a task anywhere. Stopping him at his Melbourne Park fortress is becoming virtually impossible.

Stan Wawrinka managed it in a classic quarter-final in 2014, the Swiss ending Djokovic’s bid for a fourth consecutive title before going on to claim the trophy for himself.

Some suggested Wawrinka’s breakthrough heralded the end of the dominance of the ‘Big Four’, the annual parcelling of grand slams between Djokovic, Roger Federer, Rafa Nadal and Andy Murray.

And while Wawrinka denied Djokovic a calendar grand slam with victory in last season’s French Open final, the Serb has all but carved up the men’s game for himself.

Fatherhood has not slowed Djokovic’s pursuit of silverware and at the age of 28, the best may be yet to come.

His straight sets demolition of Nadal in this month’s Qatar Open final was praised as “perfection” by the Spaniard and Djokovic admitted seeing the ball “as a watermelon”.

2016 is just 15 days old but Djokovic is already being tipped for the calendar slam.

“Yeah, if he wins the Australian, he wins all four,” seven-time grand slam champion Mats Wilander told ESPN. “He just missed (last) year, and I think that will motivate him to go all the way.”

FIFTH TIME LUCKY

Tellingly, his rivals talk more about Djokovic failing to reach top form than the standard of their own performance when asked how to get the better of the Serb.

“Maybe he has a drop-off, it’s very difficult to maintain that level for such a long period,” said second-seeded Briton Murray, who was beaten by Djokovic three times in the final including last year’s decider.

Scarred by four fruitless trips to the final, two-time grand slam champion Murray will hope for ‘fifth time lucky’ if he reaches the final.

The Scot enjoys a kind draw, with eighth seed David Ferrer the highest-ranked in his quarter, and at least boasts the physical fitness to go toe-to-toe with the Serb.

Blessed with one of the game’s most potent backhands, fourth seed Wawrinka also has weapons to trouble Djokovic and should make a deep run on the hard courts if in form.

His compatriot Federer remains an inspiration to tour veterans and his appearances in last year’s Wimbledon and U.S. Open finals were testament to the 17-times grand slam champion’s endurance.

But unlocking the secret to winning three sets against potential semi-final opponent Djokovic on 34-year-old legs may prove beyond even the Swiss master.

Unlucky to find himself in the same quarter of the draw as Wawrinka, 14-times grand slam Nadal looms as a dark horse, arriving in Melbourne the fittest he has been in years and stinging from a season without a major trophy.

Local fans will also farewell former world number one Lleyton Hewitt, the two-time grand slam champion signing off with a record 20th appearance in the men’s draw.