Rafael Nadal
File photo of Rafael NadalClive Brunskill/Getty Images

Tennis ace Rafael Nadal said on Thursday (December 28) he will be starting preparation for the upcoming Australian Open in the first week of January in Melbourne.

Nadal confirmed his plans shortly after revealing he will not take part in any tournaments in the lead-up to the next year's first Grand Slam event, starting January 15.

Knee injuries had troubled Nadal in the past and it came back to haunt him towards the end of 2017 season as he was forced to pull out of Paris Masters and the season-ending ATP World Tour Finals.

The 16-time Grand Slam champion added he will not take part in Brisbane International, starting December 31 as he is "still not ready" after a long season in 2017.

Nadal had earlier pulled out from Fast4 exhibition event, also featuring Alexander Zverev, Grigor Dimitrov and Nick Kyrgios, on January 8.

"I am sorry to announce I won't be coming to Brisbane this year. My intention was to play but I am still not ready after last year's long season and the late start of my preparation. I had a great time there and it was a great start to the month I spent in Australia," Nadal wrote on Twitter.

He added: "I will be seeing my Aussie fans when I land on the 4th in Melbourne and start there my preparation for the Australian Open."

Concerns remain over Nadal's fitness as a lot is expected of him, especially after the dream comeback run in 2017.

With rivals Novak Djokovic, Andy Murray and Stanislas Wawrinka getting back to the circuit after shortening their seasons, the Spaniard needs to be on top of his game -- both physically and mentally -- in order to retain his numero uno tag.

Dream run in 2017

Notably, Nadal made a return to the circuit earlier this year at Brisbane International after ending his season early in 2016. The Spaniard reached the quarter-final of the tournament, in which he was ousted by Milos Raonic.

Weeks later, Nadal was playing the final of the Australian Open against his nemesis Roger Federer. As it turned out, he ended up finishing second best in a marathon thriller that went on for three hours and 38 minutes.

Nadal then ended his two-year major title drought at the French Open last year and also captured the US Open to end the season on top of ATP Rankings.