Abu Dhabi, Dec 27 (AFP) Rafael Nadal is "confident" he will be 100 percent fit when the Australian Open starts in less than three weeks' time despite enduring yet another tough battle with injuries over the past few months.

The Spanish world number two had to pull the plug early on his 2018 season and has not played since a knee problem forced him to retire during his US Open semi-final against Juan Martin del Potro in September.

He underwent surgery on his ankle to remove an intra-articular loose body in November and only resumed training two weeks ago.

Nadal will dip his toes back into competition at the Mubadala World Tennis Championship exhibition in Abu Dhabi, where he faces either Kevin Anderson or Chung Hyeon in his opener on Friday.

"I started two weeks ago and of course doing the things step by step and I think I have time to be ready for Melbourne at my 100 percent," Nadal told reporters in the UAE capital on Thursday.

"It's going to be good to have some matches before but I'm confident that I'm going to arrive to Melbourne with the right situation."

The 32-year-old retired during matches at two of the four Grand Slams in 2018, but still added a record-extending 11th French Open crown to his collection.

He says he remains motivated to launch yet another comeback from injury, despite a career plagued by physical problems.

"After the second part of the year, have been tough last year in terms of injuries but that happens and that's part of my tennis career too," he added.

"Just try to stay calm, try to work the right way and when I'm back I know things are not easy, I know at the beginning you always have tough feelings and pains in the body that normally you don't have.

"But I have experience in all of this and try to be ready for the everyday practices and when (I) arrive (at) the matches I don't have to ask myself big things at the beginning, just trying to be positive with every improvement and that way normally you get the right point."

- Djokovic enjoying tennis again -

Joining Nadal in Abu Dhabi is the man who replaced him at the top of the rankings, Novak Djokovic. The Serb is the reigning Wimbledon and US Open champion and will be looking to win a third major in a row at the Australian Open next month.

Djokovic ended a two-year Grand Slam title drought at Wimbledon in July and has lost just three matches since.

He admits that he lost his motivation during the difficult period that followed the 2016 French Open, where he completed the career Grand Slam, but has now found different ways to attain gratification from the sport.

"I feel I'm not prioritising success on the tennis court for the sake of the success only as I used to do that probably up to five years ago," Djokovic said.

"For me, tennis is more of a platform now for other things and for the values I want to share, and the messages I want to share with the young generation.

"Ultimately a tennis court for me is a place where I get challenged in every possible way emotionally and my character is kind of on the line. I treat that as my own personal school of life.

"Not many places can trigger me in a positive or negative way as a tennis court does."

Djokovic takes on either Karen Khachanov or Dominic Thiem in Abu Dhabi on Friday and officially kicks off his 2019 season at the Qatar Open in Doha next week. (AFP) AH

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