Australian Open 2018: Novak Djokovic out of Australian Open as Hyeon Chung secures stunning win

Novak Djokovic has been beaten in the fourth round of the Australian Open by world number 58 Hyeon Chung.

The Serbian, a six-time Melbourne champion, was stunned in straight sets [7-6, 7-5, 7-6] by the 21-year-old South Korean.

Djokovic arrived down under unsure of how his body and his game would hold up having not played since Wimbledon because of an elbow injury.

It was a mixed bag over the first three rounds, with his remodelled service action at times vulnerable, but there had been no clue his elbow had been a problem until he called for the trainer after losing the opening set 7-4 to Chung on a tie-break.

Djokovic had fought back from a horrible start, in which he served four consecutive double faults and lost the first four games, to make it 6-6 but then played a wild tie-break.

The pain and frustration was evident as Djokovic then lost the opening three games of the second set, swiping angrily at the ball and making no effort to chase down several shots.

All of which was to take nothing away from Chung, who is enjoying his best run at a slam and knocked out fellow young star Alexander Zverev in the last round.

The Korean won the inaugural Next Gen Finals in Zverev's absence in November and, if he can continue this form, could be challenging for the biggest titles very soon, perhaps even this fortnight.

He will certainly be favourite in the next round against American Tennys Sandgren, an even more unlikely quarter-finalist following his upset of Dominic Thiem.

To his credit, Djokovic refocused and fought back to level at 4-4 in the second only for Chung to force a set point and take it after a memorable rally where he repelled everything the six-time champion could throw at him before Djokovic netted.

The Serbian at times looked like the old Djokovic but too often, and especially at big moments, he threw in uncharacteristic errors that betrayed turmoil in his mind. He fought back from 3-1 down in the third set and should have broken for 4-3 only to miss a volley with the whole court open.

Chung, meanwhile, looked completely nerveless on the biggest stage of his career and held firm to force another tie-break.

A quiet character, he was whipping up the crowd after winning another superb point with a forehand pass to lead 5-3 and when Djokovic drove a backhand wide on the Chung's first match point, the upset was complete.