Melbourne : Novak Djokovic admitted he was on the brink of defeat with dizziness and dehydration before coming through a five-set thriller against Dominic Thiem to clinch a record eighth Australian Open crown and return to world number one on Sunday.

The indomitable Serb stretched his unbeaten streak this season to 13 but he had to rally from two sets to one down to beat the courageous fifth-seeded Austrian 6-4, 4-6, 2-6, 6-3, 6-4 in a nearly four-hour marathon.

It was his 17th Grand Slam title, moving him within two of Rafael Nadal and three of Roger Federer on the all-time list.

“Definitely one of the toughest finals I have ever had in Australia,” said Djokovic, who pulled alongside Nadal (12 at the French Open) and Federer (eight at Wimbledon) as only the third man ever to win eight or more titles at the same Slam.

“I was on the brink of losing the match, I didn’t feel that good. Dominic was dominating from the baseline… then I regained the strength to pull through in the fourth set, and in the fifth, it was anyone’s game,” he added.

The victory ensured Djokovic will once again be world number one when the new rankings are released on Monday, displacing Nadal. Federer remains third with Thiem moving up a place to a career-high fourth.

But it wasn’t easy with the lethargic Serb looking out for the count in sets two and three before he regained his mojo after a medical timeout to grind down the talented Thiem.

Djokovic said he felt dizzy and sapped of energy, with the trainer telling him he was dehydrated.

“My energy completely collapsed. When I was tossing the ball I started to feel dizzy… I couldn’t believe what was happening,” he said.

Djokovic had never before won a Slam final in seven previous attempts when finding himself two sets to one down.

“If you play a Grand Slam final against him, it’s always going to be a match where very small details decide it,” said Thiem.

The Serb, 32, was the overwhelming favorite, but the supremely fit and fast Thiem, 26, always had the weapons to trouble him, which he deployed successfully for much of the match, taming his serve and unleashing some explosive groundstrokes.

However, it was a nerveless start from Djokovic, who comfortably held then put big pressure on the Austrian’s serve to get an immediate break and the psychological edge after some monster rallies.

Thiem, though, is as strong mentally as he is physically and he finally got on the scoreboard after another tough service game.

And against the run of play, with Djokovic seemingly in control, he broke back, unleashing pinpoint groundstrokes.

But the world number two was unrelenting, breaking again on a double fault as Thiem served to stay in the set.

Remarkably, a rare Djokovic double fault handed Thiem a break to go 2-1 up in set two with the Serb getting frustrated, looking at his coaching box and pointing at his head.

He refocused and once again began attacking the Thiem serve, breaking back for 4-4.

But two-time warnings on his serve in the next game rattled him and he was broken again, with the Serb patting the umpire’s foot at the changeover and telling him sarcastically: “Great job… you made yourself famous.”

With Djokovic still looking distracted, Thiem served out the set the first the Serb had dropped in an Australian Open final since 2015.

Djokovic appeared dejected and was broken twice in set three as Thiem raced to a 4-0 lead, having reeled off six games in a row.

The Serb was heard telling a trainer he was tired and after losing the set, he went for a medical timeout.

He came back revitalized and the fourth set went with serve until a Thiem double fault handed the Serb two break points and he converted to regain control.

Djokovic drew on all his experience to force another break in the deciding fifth set to take a 2-1 lead, and he kept his foot on the gas to claim an eighth crown from the last 13 Australian Opens.