But the Spanish star said Saturday he feels good and his motivation remains strong.
Nadal, who is gunning for a 17th major title but only his second Australian Open crown, was hampered by a knee injury at the tail-end of the 2017 season.
It forced him to skip the lead-up Brisbane International this month, and he has only had a one-match workout at the exhibition Kooyong Classic in Melbourne ahead of the Grand Slam starting Monday.
Yet he is unfazed and raring to go as seeks to go one better than last year when he lost an epic Melbourne Park final to Roger Federer.
"Is the first time I am here without playing an official match in my career. It's a new situation for me. But I feel good," said the 31-year-old, who played his first Australian Open in 2004.
"I feel that I had a good week-and-a-half of practices. I really hope to be ready. I feel myself more or less playing well."
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.
It saw Nadal play Austrian world number five Dominic Thiem this week on a practice court under full match conditions, with ball kids, scoreboard, and umpire.
"I wanted to play a couple of close competition matches. I played in Kooyong once. The club in Kooyong is great, but at the same time the conditions of play are completely different from here," he explained.
"That's my feeling. We decided to play another match. Talking with the Australian Open, yeah, they gave us the chance to play like an open practice but closer to the match for the crowd.
"We did it. It was a good practice, good feelings for both of us I think. The job was done the right way."
- Healthy and competitive -
Despite his achievements in a long career, motivation for Nadal, who needs to reach the quarter-finals to be certain of retaining his world number one ranking, with Federer breathing down his neck, remains undiminished.
Not only can he clinch a 17th Grand Slam in Melbourne, but he also has the opportunity to join Roy Emerson and Rod Laver as only the third man in the Open era to win each of the four Grand Slams twice.
The only place he is yet to achieve the double is Australia.
"For me, the Australian Open always, if you are not 100 percent motivated to play this tournament, you probably you don't love this sport," he said.
But he knows anything can happen so early in the season, despite being the top ranked player in the world.
"Everyone starts from zero. I start from zero again," he said.
"It's the start of a new season, an exciting one. I hope to be healthy and competitive, and most important thing, I hope to enjoy tennis one more year."
In Melbourne, Nadal is at his first major tournament in years without his uncle Toni, who coached him from childhood until after his US Open win last year.
Toni Nadal is now coaching at the Rafael Nadal Academy, with his nephew under the tutelage of Carlos Moya.
"In terms of professional things, I spoke to him few days ago, speaking about how the life going, how the tennis going," he said of Toni.
"If I have something to ask, I ask him. If he have something to tell me, he call me and tell me."