Meanwhile, 2017 Australian Open champion Serena Williams opted out of the competition, saying that her preparations had fallen just short of what she needed to be competitive after giving birth in September.
While there are many major sporting events that grace the stadiums and streets of the Victorian capital of Melbourne, Australia, none have a bigger impact on the city than the Australian Open.
No one was able to get anywhere close previous year, not just in terms of consistently winning the biggest tournaments but also when it comes to charisma.
"There was a doubt, especially after I pulled out of the first week of the year", said Djokovic, who had not played since retiring in the Wimbledon quarter-finals last July.
Nadal's first official match is scheduled to take place at the Australian Open, following his withdrawal from the Brisbane International tournament and from an exhibition held in Abu Dhabi.
Nadal, 31, heads the entry list for the Australian Open and said he will be ready to front up for the first round.
Bookmakers are tipping the world No. 2 and tournament's second seed to win the title at A$2.75 (S$2.88).
"I'm just excited going back to Melbourne where I had my fairytale run previous year".
"I have felt pain in my right adductor since I started practising here". The Dane will also look to improve upon her record of semi finals in 2011 and win her first ever Grand Slam title.
Third-seeded Muguruza is in a hard quarter containing former Australian Open champions Maria Sharapova and Angelique Kerber, and U.S. Open finalist Madison Keys. His only regret was losing the number one rank to Rafael Nadal who confirmed his status by reaching the quarter-finals of the Paris Masters before eventually retiring with a knee problem.
"I don't want to be over-confident, but I'm very, very happy with how it went today".
"If I got to play the way I did yesterday against the number five in the world".
However, perhaps the most significant indicator of who could shine brightest in 2018 came in October when Caroline Wozniacki battled to a maiden WTA Finals title, displaying a new brand of ruthless tennis that suggested a first grand slam was imminent.