MELBOURNE, Australia (AP) — Novak Djokovic has that unbeatable feeling.

And well he should.

The Serb outlasted Rafael Nadal to defend his Australian Open title in the longest ever Grand Slam final and become the fifth man to win three straight majors in the Open Era.

Djokovic now has the French Open — the one major to elude him — in his sights. He won’t even rule out the ultimate: the Grand Slam.

“One player (Rod Laver) has done it, so it is possible,” he said after the traditional post-victory photo shoot in a downtown Melbourne park on Monday. “Obviously the times are different and tennis nowadays is much more competitive and much more physical. And that makes that challenge more difficult to achieve. But everything is possible.”

With the London Olympics to follow Wimbledon this year, Djokovic could even make it a Golden Slam by winning the gold medal at London 2012 to go with the four majors.

“The facts are that I’m at the peak of my career,” Djokovic said. “I feel physically and mentally at the peak, I feel strong, I feel motivated, I feel eager to win more trophies.”

Having slept for only a few hours, Djokovic dispensed with the band and the raucous dressing room celebrations that marked his victory last year, choosing to strum the air guitar and belt out a few lyrics from “Highway To Hell.”

Djokovic recalled the brief celebrations after the match at Rod Laver Arena and made a half-hearted attempt to sing the refrain from the AC/DC rock anthem. His legs were too tired, and his throat a bit hoarse. “Oh man, I’m tired.”

And so he should be. Djokovic completed a 5-hour, 53-minute 5-7, 6-4, 6-2, 6-7 (5), 7-5 victory over Nadal at 1:37 a.m. — ending an epic match with a forehand winner that finally finished off the Spaniard.

He defied exhaustion to tear off his shirt and flex his bare torso as he made his way to celebrate with friends and family. He was still doing interviews after 4 a.m.

It didn’t leave much time for celebrating. Unlike his victory at the 2011 Australian Open, when he beat his friend Andy Murray in straight sets and then kicked off an all-night party with a rock band in the locker room.

“I didn’t have any more energy left to celebrate,” Djokovic said Monday. “I was preferring my bed.”

When he awoke not long after, his body reminded him not just of the incredible events of the previous evening, nearly six hours of physically punishing tennis against one of the game’s most ferociously competitive athletes, but also of a near five-hour semifinal two nights earlier against Murray.

“I felt lots of pain all over the body,” he said. “The adrenaline is still there and I still am very excited about what I have experienced here in the last two weeks and especially last night. I’m full of joy, but I think still I don’t have a real sense of what’s going on.”

Djokovic wasn’t the only one feeling a little dazed Monday. There were still 1.86 million people watching in Australia until after 1:30 a.m. The peak audience was 3.86 million, approaching about one-fifth of the population. When the last ball was struck, hardly any of the almost 15,000 spectators in Rod Laver Arena had left.

A historic final provided a fitting climax to a men’s tournament that also featured riveting semifinals between Nadal and No. 3-ranked Roger Federer, and Djokovic and No. 4 Murray.

Djokovic’s seventh straight win in a final over Nadal underlined his dominance of the men’s game, which until last year had been headlined by Nadal and Federer.

Now it’s Djokovic’s turn to feel like he’s the one who can’t lose.