Tennis: Mate tips Djokovic for Oz

Novak Djokovic has been knocked off the top of the world rankings.

He has been dethroned as world No1 but one of Novak Djokovic's closest allies insists the Serb remains a firm favourite to land a record seventh Australian Open crown next month.

Battling "personal issues", Djokovic's unbroken 122-week reign atop the rankings came to an end with his loss to Andy Murray in last month's winner-takes-all World Tour Finals tennis decider.

Despite failing to add to his 12 majors since the French Open, where he became the first man since Rod Laver to hold all four grand slam crowns simultaneously, most rivals would kill for Djokovic's end to the season.

Apart from the season-ending championship, Djokovic also reached the US Open final for the seventh time and won the Toronto Masters.

But the 29-year-old's seven-title season was otherwise tainted by rumours around his personal life and early exits from Wimbledon and the Rio Olympics.

For the first time since 2014 - and only the second time in five years - Djokovic won't be top seed at Melbourne Park, where five-time runner-up Murray will instead be the hunted after his surge to world No1.

But rankings don't mean anything to Djokovic's Davis Cup teammate Viktor Troicki.

Djokovic reached out to Troicki during his low moments at the end of 2016 and revealed a renewed hunger at Troicki's wedding in Belgrade last week.

"He's always there as a great friend of mine and I'm there for him," Troicki said from Belgrade. "We've seen each other quite a bit. We're in touch always and we see each other when we have time.

"He won in Melbourne there so many times and he feels right at home and I'm sure he'll have refreshed the batteries and be a totally different player than he was at the end of 2016.

"He'll be 100 per cent ready to go for the title in Melbourne."

- AAP