Who can stop Djokovic? Australian Open's controversial king targets ninth crown

Novak Djokovic has not endeared himself to fans over the past year, but the Australian Open's undisputed king will take some stopping as he targets a record-extending ninth title at Melbourne Park.

Djokovic claimed his 17th Grand Slam crown in last year's gripping final, when he came back from 2-1 down to edge Austria's Dominic Thiem in five sets.

The Serbian's eighth victory in 16 visits reinforced his dominance in Melbourne's Rod Laver Arena, where he claimed his first Grand Slam title in 2008 and has won seven of the last 10 editions.

Rafael Nadal and Thiem look to be his biggest rivals at this year's tournament, with six-time Australian Open champion Roger Federer sidelined as he recovers from double knee surgery.

The Australian Open was the highlight of a mesmerising early 2020 season for Djokovic, who won his first four tournaments of the year.

However, off-court, things soon unravelled for the elastic-limbed world number one.

After tennis went into lockdown because of the coronavirus pandemic, Djokovic launched the ill-fated Adria Tour in June, with no social distancing and players pictured dancing shirtless at a packed nightclub.

Djokovic and his wife Jelena were among a number of people to subsequently test positive for the virus, with Grigor Dimitrov, Borna Coric and Viktor Troicki also falling ill.

Worse was to come when tennis resumed and Djokovic defaulted out of the US Open in sensational fashion, when he angrily swiped away a ball that accidentally hit a female line judge in the throat.

His hopes of becoming the first man in half a century to win all four Slams twice then ended in a straight-sets defeat to Nadal in the French Open final.

Djokovic also drew negative comment in August for launching the Professional Tennis Players Association, a breakaway group outside the men's tour, as tennis attempted to get back on its feet.

And he found himself labelled a "tool" by Australia's Nick Kyrgios after requesting better conditions for players during Australia's mandatory quarantine, including private houses with tennis courts.

Despite the off-court turbulence, Djokovic enjoys strong support in Melbourne -- which has a sizeable Serbian population -- and said Rod Laver Arena brings back "beautiful memories".

"It does feel like a home for me in Australia, in Melbourne, particularly in Rod Laver," he said this week.

"That is by far my most successful tennis court in my career. Had some profound memories in the last 15 years, and you know, won my first Grand Slam back in 2008.

"Had probably the most exciting matches played on this court, and definitely the longest match ever that I played was in the finals, almost six hours with Rafa (Nadal) in 2012."

Nadal will undoubtedly figure prominently in the tournament but it is now 12 years since he won his lone title in Melbourne, despite four more trips to the final.

The Spaniard also has fitness concerns after he pulled out of two days' play at this week's ATP Cup with a sore back.

Thiem came agonisingly close to victory last year and, buoyed by his first Grand Slam title at the US Open, will be confident against anyone in the draw -- including Djokovic, against whom he has won five of their last seven meetings.

Alexander Zverev, Daniil Medvedev and Stefanos Tsitsipas are also among the top contenders at a tournament where form is difficult to judge, with playing opportunities hard to come by during the pandemic.