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.

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.

Stanislas Wawrinka managed it in a classic quarterfinal 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, Rafael 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.

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.

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 US Open finals were testament to the 17-times Grand Slam champion's endurance.

But unlocking the secret to winning three sets against potential semifinal 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.

Serena favourite

Ailing knees, Father Time and even a resurgent Victoria Azarenka stand in the way of Serena Williams clinching her seventh Australian Open title and giving her one more shot at an achievement that would cap her storied career.

Williams had the opportunity last year to clinch the only feat missing from her resume and become the first female player since Steffi Graf in 1988 to capture a calendar Grand Slam at the US Open.

Victory at Flushing Meadows would have moved her into a tie with Graf on 22 Grand Slam titles, the most in the Open era, and two behind the all-time leader, Australia's Margaret Court.

Instead, knees that were constantly causing her pain and a sore elbow that reduced the power on her serve and groundstrokes, ended her hopes in the semifinals.

She skipped the remainder of the year to recuperate, also indicating the mental pressure to achieve the Grand Slam had taken a toll as she admitted her heart had been broken by the defeat to Italy's Roberta Vinci.

Williams will also be casting a glance towards the resurgence of Azarenka, who has had a tormented two years with foot injuries and a downward spiral in the rankings.

The Belarusian, who won successive Australian Opens in 2012 and 2013, however, stormed to victory in Brisbane last week as she dropped just 17 games over five matches to claim her first title since the Cincinnati Masters in August 2013.

She is one of the few players with the power and speed to consistently challenge Williams, who she pushed to a deciding set in each of their three matches last year while ostensibly still on the comeback trail.

The aggressive, power-hitting Garbine Muguruza heads the swag of young pretenders looking to finally usurp Williams, with second seed Simona Halep and fourth seed Agnieszka Radwanska also in contention.

Two veterans are also in the mix — multiple Grand Slam winners Maria Sharapova and Serena's older sister Venus. The Russian has an arm injury and is drawn to face the world number one in the quarterfinals.