Rafa Nadal's hopes of a 15th grand slam title were crushed by an inspired Roger Federer in the Australian Open final on Sunday but the rejuvenated Spaniard was already rubbing his hands together with the prospect of a "special" season on clay.

Nadal battled back twice from a set down and held a 3-1 lead in the deciding fifth but was powerless to stop Federer's victory charge and bowed out 6-4 3-6 6-1 3-6 6-3 at a heaving Rod Laver Arena.

Although defeated for the championship, the 30-year-old lefthander won a huge measure of self-belief, having reached his first grand slam final since his 2014 French Open victory.

The tournament was a major test of his fitness after a wrist injury wrecked his 2016 season and the signs were good, said Nadal, who will bid to extend his record haul at Roland Garros to 10 titles in May.

"I cannot predict what's going on in the future," mused the Mallorcan, who was seeded ninth at Melbourne Park.

"I just think that I am playing well.

"I believe that playing like this, good things can happen. (They) can happen here on this surface, but especially can happen on clay.

"On clay I (can) recover better than here, then the opponents don't get that many free points, and I am playing from the solid baseline.

"If I made that happen, I think I can keep having success in hard courts, but on clay can be special."

Six-times champion Novak Djokovic was conveniently eliminated from his Nadal's half of the draw early in the tournament, but the Spaniard still had to negotiate a perilous run to the final.

He had to weather five-set marathons against German wunderkind Alexander Zverev in the third round and rising Bulgarian Grigor Dimitrov in the semi-finals.

He also thrashed third seed Milos Raonic in their quarter-final to leave few in doubt that he was back to a level approaching his best.

Prevailing in the epics was the most encouraging, said Nadal, feeling that he had the mental and physical strength to handle the rigours of the grand slams.

But he admitted that he was feeling the pinch when taken into the fifth set by Federer, who won his 18th grand slam title.

"It's true that I probably (lacked) a little bit of speed today compared to the last day in my legs probably, a little bit. But that's normal after what happened one day and a half ago," he said of the five-hour semi-final against Dimitrov.

"I think I tried. I didn't play bad. But it's true it was difficult to play a lot because he really went for the shots, almost for every shots."

Although losing five straight games to surrender the title, Nadal hardly lay down.

He saved nine break points in the fifth set and a match point, forcing Federer to rip the match from his hands with aggression and brilliant shot-making.

"I am with big personal satisfaction. I cannot say that I am sad," said Nadal.

"I won against the best players of the world, and I competed well against everybody. That's the most important thing for me, and that gives me confidence to keep playing, and that's what I am going to try."