Rafael Nadal insisted his run to the Australian Open final was "completely unexpected" after moving to within a win of a record-breaking grand slam title.

Nadal, 35, overcame Matteo Berrettini 6-3 6-2 3-6 6-3 in their semi-final under the Rod Laver Arena roof on Friday.

After doubts over his career due to a persistent foot injury, Nadal is into a 29th grand slam final and a win away from a 21st major crown, which would break a tie with Roger Federer and Novak Djokovic for the most won by a man.

The Spaniard said he had no expectations to reach the decider in Melbourne, where Daniil Medvedev or Stefanos Tsitsipas await.

"For me it's something completely unexpected, so I am super happy. Of course everybody knows me, and I'm always going to try my best. Of course my goal now is to win," Nadal told a news conference.

"As I said, for me, it's a present, just be here and play tennis. I am taking now things a little bit in a different way, of course always with competitive spirit that I have, because I can't go against that. It's my personal DNA.

"But in some way, I don't know, just be what I am and be able to have the chance to compete at this level, it's a positive energy for me to keep going, because at the end of the day, and being very honest, for me it's much more important to have the chance to play tennis than win the 21. Because that makes me more happy in terms of general life to be able to do the thing that I like to do more than achieving another grand slam.

"At the end of the day, life, it's about happiness and what makes me happy. It's about just having the chance to do what I like to do."

Rafael Nadal graphic

Nadal ended his 2021 season in August and, after a four-month absence, returned for an exhibition event in Abu Dhabi last month.

He claimed his 89th ATP Tour title in Melbourne earlier this month before progressing to the Australian Open final.

"I feel alive in terms of my tennis life, you know, in terms of my tennis career," Nadal said.

"In my personal life, I honestly have a good life. I feel lucky that my family is healthy, and during these challenging times that's everything. More important than tennis, for sure. 100 per cent.

"But, yeah, I explained before, for a long time I wasn't able to practice. Sometimes I went on court and I was able to practice 20 minutes, sometimes 45, sometimes zero, sometimes two hours, but have been very, very rough in terms of imagining myself playing at the best-of-five at this moment.

"So, yeah, I don't know. Super happy. It's true that I worked hard for a long time every single day in terms of when I was not able to play tennis I was working hard in the gym.

"I think I'm never going to say I deserve, because a lot of people deserve. But I worked the proper way, and I hold the positive spirit and attitude to have the chance to give myself a chance to be back."