Novak Djokovic and Rafael Nadal kickstart their 2023 campaigns this week in Adelaide and Sydney respectively, with the superstar veterans and great rivals eyeing up yet more Australian Open glory. With the pair sharing 43 Grand Slam titles between them -- Djokovic has 21 and Nadal 22 -- the scene is set for an epic showdown at Melbourne Park in January. Nadal is the defending Australian Open champion and Djokovic is a nine-time winner. Djokovic returns Down Under for the first time since being sensationally detained and then deported ahead of the 2022 Australian Open because of his refusal to get vaccinated for Covid-19. He starts his bid for an incredible 10th Australian Open title at the Adelaide International from Sunday, following a troubled and truncated year in which he missed two majors because of his vaccine status. Djokovic was initially barred from entering Australia before 2025, but a new government in Canberra reversed the ruling and he is now gunning for more silverware at his most successful Grand Slam venue. "Over the years I've been really fortunate to start very strong in Australia and I love playing there," said the world number five in Dubai last week, after ending 2022 with a record-equaling sixth ATP Tour Finals crown. "After obviously what happened earlier this year, hopefully I can have a decent reception there and hopefully that can help me play some good tennis." He will face a top-notch field in Adelaide, including Felix Auger-Aliassime, Daniil Medvedev and Andrey Rublev, ranked six, seven and eight respectively. In Djokovic's absence this year, Spanish great Nadal swept past Medvedev to win the Australian Open in an epic five-setter -- then backed it up with a 14th French Open. 'A lot of hours on court' Nadal will begin his preparations in Sydney at the United Cup, a new mixed-teams event, where a blockbuster showdown with Australian showman Nick Kyrgios will test his credentials. Eighteen countries will compete in the event across 11 days from Thursday, with Brisbane, Perth and Sydney hosting group games in a round-robin format. Ties comprise two men's and two women's singles matches and one mixed doubles. The finals series will be played in Sydney. World number three Casper Ruud and Germany's Alexander Zverev, who is returning from a serious ankle injury, will participate. Top-ranked Carlos Alcaraz will warm up at the Kooyong Classic exhibition in Melbourne from January 10-12 as he battles back from the abdominal injury that shortened his pre-season training block. The 19-year-old Spaniard, a major threat to Djokovic and Nadal, missed the season-ending ATP Finals and Davis Cup Finals with a muscle tear, but is confident he will be ready. "I would say the key is to practice a lot, spend a lot of hours on court," he said this month. "I will be ready and 100 percent heading into Australia." Italy's Jannik Sinner and world number nine Taylor Fritz, among others, will also use Kooyong to fine-tune. Women's world number one Iga Swiatek will acclimatize in Perth with her Polish teammates at the United Cup on the back of winning the French Open and US Open in 2022. The three-time Grand Slam champion is targeting a first Australian Open title after losing in the semis this year to Danielle Collins, who then crashed to Ashleigh Barty in the final. Swiatek inherited the top ranking following the shock retirement of Barty in March, and has been dominant ever since. American world number three Jessica Pegula and resurgent French world number four Caroline Garcia, fresh from beating Aryna Sabalenka to win the WTA Finals, also feature at the United Cup. Four of the other top 10 women begin the year in Adelaide, with second-ranked Ons Jabeur, world number five Sabalenka, world number eight Daria Kasatkina and world number nine Veronika Kudermetova all entered.