For all of his standing as a dominant force on the men’s tennis tour in recent years, Novak Djokovic had an even more formidable aura of invincibility at the Australian Open.

The reigning champion had won six of the past nine titles at Melbourne Park, and had never failed to reach the final eight in that time.

Which made this year’s second-round loss to Uzbek wildcard Denis Istomin all the more remarkable.

The Serbian second seed had no excuses for his 7-6 (10-8) 5-7 2-6 7-6 (7-5) 6-4 loss over a gruelling four hours and 48 minutes.

“You know, that’s sport,” he said.

Rather he offered a typically classy, if somewhat cryptic, tribute to the world No.117, who had never previously beaten a player inside the top 10.

“All I can say is hats down,” Djokovic said. “I didn’t really have a clear chance, to be honest. Wherever he needed, he came up with big serve, big play. He deserved to win.”

Istomin, who has never been ranked higher than No.33 in the world, agreed after the match that the win was the highlight of his 13-year career.

“It’s unreal,” Istomin said. “For me, it was impossible to think that I can hold it five sets with Novak, physically and mentally. So I did well today.

“It means so much for me to beat the world No.2.”

Istomin’s form coming into this tournament did nothing to hint at a career-best performance: he lost to world No.211 Christian Garina in a Challenger event in Bangkok.

But the 30-year-old said defeating Djokovic gave him the confidence to “feel like I can play with these guys and be on their level”.

Denis Istomin celebrates his biggest win of his career. Photo: Getty

While Istomin will progress to a third-round match against 30th seed Pablo Carreno Busta of Spain, Djokovic will face fresh scrutiny about his mindset and motivation.

After winning his maiden French Open last year to complete a sweep of grand slam titles, his form tailed away in the second half of the season, only for him to bounce back by opening 2017 with a victory over world No.1 Andy Murray in the Qatar Open final.

“I’m not used to losing in the Australian Open second round,” Djokovic lamented.

“I’ve always played so well. I’ve won six titles here. This court has been so nice to me. I enjoyed it very much.

“Of course, it’s disappointing. But at the end of the day I have to accept it.”

Denis Istomin feels like he reached a new level! #AusOpen pic.twitter.com/Cdw3eCTGh4

— #AusOpen (@AustralianOpen) January 19, 2017

Maybe, as Djokovic noted, this was just one of those days that sport throws up every now and then.

And in his case, that day was now but rarely then.

Djokovic has only lost once to a player ranked outside the top 100 in the past seven years, and that was to dangerous No.145 Juan Martin del Potro at last year’s Olympics.

He had not failed to make the third round of a major since Wimbledon in 2008 and this was his earliest exit from Melbourne Park since his first-round loss in 2006.

For Istomin, who was only in Melbourne after winning the Asia-Pacific wildcard playoff, it was also one of those days.

“Sometimes you have a good feeling,” he concluded. “At this moment everything is good. The body, emotions, the game was in one.”

Dasha does it in three

Australian Daria Gavrilova has declared she’s a better player than during last year’s charge to the Australian Open fourth round.

But the 22-year-old Australian is refusing to get carried away with her title prospects despite reaching the third round with a hard-fought 6-2 1-6 6-4 win on Thursday night over Croatian teen Ana Konjuh.

She joins comeback queen Ashleigh Barty in the last 32.

Ranked No.23, Gavrilova next faces Swiss 12th seed Timea Bacsinszky, who she has beaten in their two previous meetings.

“I’m not thinking about the future. I’m just being in the moment right now,” she said.

Asked whether she was playing better than last year, when she achieved her best result at a major tournament, Gavrilova said: “I think I’m a better player, yeah.”

Two Australians will play in the Open third round for the first time since 2014. Photo: Getty

She felt her physical game, as well as mental strength, was tracking well.

“I’m happy with the way I’m playing right now,” Gavrilova said.

“There’s nothing much to improve – just a few tactical things against players that I’m playing.”

Everything was going her way in the early going, as the hard-hitting Croatian struggled to find her range, hitting 26 unforced errors in the opening set.

Daria Gavrilova through to the third round! #AusOpen pic.twitter.com/HP1xGddYvG

— #AusOpen (@AustralianOpen) January 19, 2017

With a mix of brilliance and speed, including a cheeky baseline drop shot, the 26th seed stormed away with the first set.

The Australian’s frustrations, however, became evident in the second, dropping a double break and soon her racket, as Gavrilova lost the set and her cool.

Konjuh’s raw power and blazing groundstrokes set up the decisive third and final set, before Gavrilova swung momentum once more with her trademark baseline game.

An all-important break in game six – the 10th break of serve for the match – gave Gavrilova the advantage in the see-sawing contest on Hisense Arena. Staving off two vital breaks the following game, she served out the match.

Meanwhile, Aussie Jordan Thompson fell to a four-set loss to eighth seed Dominic Thiem 6-2 6-1 6-7 (6-8) 6-4, while wildcard Andrew Whittington was bounced out of the Open in straight sets by 20th seed Ivo Karlovic. The big-serving Croat powered past Whittington, 23, winning 6-4 6-4 6-4 in two hours.

-with agencies