San Francisco Frontiers - Djokovic confronts heckler as he battles through at Australian Open

The world number one showed his trademark mental strength to face down his inspired opponent, prevailing 6-3, 4-6, 7-6 (7/4), 6-3 in more than three hours.

It followed a gruelling first-round match on Sunday, when he was kept on court for more than four hours by teenager Dino Prizmic, admitting afterwards he was "a bit under the weather".

The Serbian got drawn into a testy exchange with a spectator on Rod Laver Arena early in the fourth set on Wednesday.

"There were a lot of things that were being told to me on the court... I was tolerating it for most of the match," he said.

"At one point I had had enough, and I asked him whether he wants to come down and tell it to my face.

"When you confront somebody, unfortunately for him, he didn't have the courage to come down.

"That's what I was asking him. If you have courage, if you're such a tough man, tough guy, come down and tell it to my face, and let's have a discussion about it."

The top seed was asked whether the argument had fired him up.

"Maybe that was needed," he said. "I don't know. Look, I don't want to be in those types of situations. Yeah, I was flat I guess emotionally.

"Game-wise I was quite flat for some part of the match, end of second set, most of the third set.

"Maybe that was needed for me to be shaken up a bit and start to find the kind of intensity on the court that I needed to have all match."

- Drama -

The start of the contest did not hint at the drama that was to follow as the 10-time champion cruised through the first set.

But his unforced error count ticked up in the second set and he was broken for the first time in the fourth game.

Popyrin appeared to have blown his chance to level when he produced a sloppy service game when serving for the set.

However, Djokovic, again looking out of sorts and blowing his nose during changeovers, failed to build on his break and the Australian produced an impressive backhand lob to level the match, urging the crowd to up the volume.

Popyrin asked for a medical timeout when leading 3-2 in the third set and received treatment on his left calf, accompanied by a Mexican wave among the fans.

The pivotal point in the match came in the 10th game.

Three uncharacteristic unforced errors from Djokovic's racquet gave Popyrin three set points but he was unable to capitalise.

The 24-year-old Australian also missed out on a fourth opportunity as the top seed levelled in a game lasting nearly 10 minutes.

Djokovic, 36, won the tie-break to take a firm grip on the match as Popyrin received more treatment on his leg.

The Serbian re-focused after his altercation, breaking to love in the sixth game of the fourth set, which proved decisive.

Djokovic, with 24 Slams under his belt, is already the most decorated player in the men's game -- two clear of the injured Rafael Nadal and four ahead of the retired Roger Federer.

He is gunning for an 11th Australian Open title to pull clear of Margaret Court on the all-time list of majors and will next meet Argentine Tomas Martin Etcheverry.

O.Green--SFF