View Photo Gallery: Novak Djokovic will defend his Australian Open title in Sunday’s final in Melbourne.

For most of 2011, Novak Djokovic was simply unbeatable.

The 24-year-old Serb steamrolled his way to a sterling 70-6 record that included three Grand Slam titles.

In Friday’s Australian Open semifinal, Andy Murray appeared poised to knock the world’s top player from his perch — but it seems Djokovic is not ready to relinquish his throne.

After falling behind two sets to one, a visibly drained Djokovic stormed to a fourth set win, then outlasted Murray in a thrilling fifth set to claim a 6-3, 3-6, 6-7, 6-1, 7-5 victory. With the win, Djokovic will face Rafael Nadal in Sunday’s final. It will be the third straight Grand Slam final pairing the world’s two top-ranked players.

The loss is the latest heartbreaking result for Murray, who has yet to break through for his first major title, despite reaching three finals, including the last two in Melbourne.

Andy Murray left it all on the court, but came up short yet again. (William West/AFP/Getty Images)

“Andy deserves the credit to come back from 2-5 down. He was fighting. I was fighting,” an exhausted Djokovic said after the match. “Not many words that can describe the feeling of the match.

“Evidently it was a physical match ... it was one of the best matches I played. Emotionally and mentally, it was equally hard.”

Djokovic, who admitted he had difficulty breathing through his nose during a quarterfinal win over David Ferrer, again appeared to struggle physically during the match. He has Saturday off to prepare for what should be another grueling final.

“I’m going to try to recover,” Djokovic said. “Obviously it’s going to be physical as well. So I need to do some push-ups tonight.”

Now Nadal must figure out a way to get past his tormentor. Djokovic defeated the Spaniard in six tournament finals last year, including Wimbledon and the U.S. Open.

More Australian Open coverage from Washington Post Sports:

Early Lead: Nadal fends off Federer in four sets to reach final

Azarenka advances to first Grand Slam final, will face Sharapova

Kim Clijsters ousted from what may be her last Australian Open

Australian Open: Scoreboard, schedule of play