Novak Djokovic is confident he can still win Grand Slams, starting at the Australian Open, with the Serbian kickstarting his bid for an unprecedented 11th title and record 25th major crown in Brisbane this week.

Top-ranked Aryna Sabalenka, who is gunning for a third Melbourne Park trophy, joins him at the Queensland Tennis Centre from December 29-January 5 in a stellar women's field.

The 2025 season gets under way on Friday with the mixed-teams United Cup in Perth and Sydney, headlined by world number two Iga Swiatek in her first tournament since revelations that she served a one-month doping suspension.

It is the first season since 37-year-old Djokovic began playing that none of the other so-called "Big Four" will be on the other side of the net following the retirements this year of Rafael Nadal and Andy Murray.

As they faded, Jannik Sinner and Carlos Alcaraz stepped up to become the new Grand Slam kings, with both men opting against a warm-up tournament leading into the first major of the year which begins on January 12.

As doubts grew over Djokovic's motivation and ability to take down the new guard after a disappointing 2024, he stunned the tennis world by hiring Murray to coach him.

A resurgent Grigor Dimitrov, Holger Rune, and Frances Tiafoe are also playing in Brisbane, as is Australian Nick Kyrgios, who returns after injuries restricted him to just one ATP Tour singles match in two years.

Challenging Sabalenka on Pat Rafter Arena will be America's top talents Jessica Pegula and Emma Navarro, ranked seven and eight respectively, along with former world number two Ons Jabeur and veteran Victoria Azarenka.

Sabalenka, who beat China's high-flying Zheng Qinwen in the Melbourne final this year, had a sensational 2024 which culminated in being named WTA Player of Year this month. (AFP)