Despite that, Nadal, 31, said he felt in decent enough form ahead of a first-round clash against Victor Estrella Burgos.
But the Spanish star said Saturday he feels good and his motivation remains strong.
And there's been a changing of the guard in his coaching box, with his long time mentor uncle Toni Nadal leaving his official entourage at the end of previous year. "I feel myself more or less playing well".
Maria Sharapova, who triumphed at the Australian Open in 2008 and lost three finals (in 2007, 2012 and 2015) has choosen a pink and black outfit.
He played an exhibition match against Richard Gasquet at the Kooyong Classic in third-gear, stepping up his preparation with a specially-arranged practice match with Dominic Thiem on Margaret Court Arena on Friday.
"I feel that I had a good week-and-a-half of practices".
With so few matches under his belt ahead of the season-opening Grand Slam, he asked organisers if they could do him a special favour, and they obliged.
"I'll be over the moon if I can play", he said.
"We chose to start later because we needed some more practice".
Nadal finished on top of the year-end rankings after winning the French and U.S. open crowns. The job was done the right way.
Federer was coming off an extended injury break and was seeded 17th at last year's Australian Open when he beat Nadal, who was seeded ninth, in five sets in the final.
Australia's Nick Kyrgios is the sole men's seed but, unfortunately, misses out on a coveted top-16 ranking by one place. "For me, the Australian Open always, if you are not enough motivated, 100 per cent motivated to play this tournament, probably you don't love this sport", Nadal said.
But he knows anything can happen so early in the season, despite being the top ranked player in the world.
"But everyone starts from zero. I start from zero again", he said.
Take one determined old guard, throw in a mix of exciting youngsters and add in a couple of returning heroes, and you have a recipe for a thrilling contest.
Toni Nadal is now coaching at the Rafael Nadal Academy, with his nephew under the tutelage of Carlos Moya. He has enough confidence with me, or I have enough confidence with him, to talk about anything I have to talk.
"If I have something to ask, I ask him".