WATCH | Australian Open: Hyeon Chung earns sensational straight-sets win over Novak Djokovic

Six-times champion Novak Djokovic bowed out of the Australian Open in the fourth round as relentless South Korean Chung Hyeon ground him down to claim a stunning 7-6(4) 7-5 7-6(3) victory on Monday.

The 21-year-old Chung, ranked 58th in the world, proved an immovable object, absorbing everything the former world number one could throw at him and returning it with interest.

Two years after losing in straight sets to Djokovic on the same Rod Laver Arena, the bespectacled Chung turned the tables to claim the biggest victory of his career. He is also the first South Korean to reach a Grand Slam quarter-final and will be favourite to reach the semis with unseeded American Tennys Sandgren up next.

"I didn't know how I'd win tonight. I was just honoured to play against Novak and happy to see him back on the Tour," Chung said on court as his compatriots cheered in the stands. "I try to copy Novak in the way I play, he is my idol."

Djokovic wore a compression sleeve on his serving arm, a legacy of the elbow injury that sidelined him last year. The Serb grimaced occasionally and needed treatment on his feet after losing the first set.

"Congratulations to Chung on an amazing performance," the 12-times Grand Slam champion said. "He deserved to win. Whenever he was in trouble he came out with some great passing shots and at the back of the court he was like a wall."

Djokovic made a dreadful start as a spate of double-faults cost him his first two service games and he trailed 4-0. He clawed back the deficit but Chung took the opening set on the tiebreak.

Chung moved 4-1 ahead in the second set but again Djokovic recovered, only to falter when serving at 5-6, netting a forehand on set point after Chung had shown incredible defensive skills to stay alive in the rally. Djokovic battled back from a break down in the third but he inexplicably put an angled volley out when he had break point on the Chung serve at 3-3.

Chung saw a 3-0 lead disappear in the night's second tiebreak but he refused to let Djokovic off the hook. He showed miraculous court coverage to hook a mind-boggling forehand winner past Djokovic to take a 5-3 lead in the tiebreak and when Djokovic netted a return it brought up three match points. One was enough as Djokovic hit a backhand into the tramlines. 

Here are highlights

The 6x against the gritty youngster.

We're just about ready to go between @DjokerNole and Hyeon #Chung. Who have you got? #AusOpen pic.twitter.com/cVZn6DaiTn

— #AusOpen (@AustralianOpen) January 22, 2018

#Chung off to a handy start!

First break. #AusOpen pic.twitter.com/ZJtWV7PTAc

— #AusOpen (@AustralianOpen) January 22, 2018

Return to sender #AusOpen pic.twitter.com/LoStViaVqX

— #AusOpen (@AustralianOpen) January 22, 2018

#Chung is on 

Certainly not overwhelmed by the occasion.#AusOpen pic.twitter.com/DZUdmeojFS

— #AusOpen (@AustralianOpen) January 22, 2018

.@DjokerNole breaks back!

We're all tied up in the first set - 5-5#AusOpen pic.twitter.com/rNpD41fDhP

— #AusOpen (@AustralianOpen) January 22, 2018

What a performance thus far from the young  star!#Chung takes the first set 7-6(4)#AusOpen pic.twitter.com/qFwdsMsFXg

— #AusOpen (@AustralianOpen) January 22, 2018

Some intense rallying going on between the pair on @RodLaverArena!#AusOpen pic.twitter.com/V7tm103pAQ

— #AusOpen (@AustralianOpen) January 22, 2018

Running out of words to describe these #Chung winners...

He leads 2- early in the second set.#AusOpen pic.twitter.com/D4iLqALp0F

— #AusOpen (@AustralianOpen) January 22, 2018

.@DjokerNole's troublesome elbow causing a little concern for the x champ...#AusOpen pic.twitter.com/UGEGpHyrlK

— #AusOpen (@AustralianOpen) January 22, 2018

Just another #Chung special... #AusOpen pic.twitter.com/SHxnKnLNso

— #AusOpen (@AustralianOpen) January 22, 2018

.@DjokerNole must feel like he's playing a mirror-image of himself...

Hyeon #Chung  takes the second set 7-5! #AusOpen pic.twitter.com/R7096NJsrw

— #AusOpen (@AustralianOpen) January 22, 2018

This match has had EVERYTHING!

@DjokerNole#AusOpen pic.twitter.com/ZGiTl7U2su

— #AusOpen (@AustralianOpen) January 22, 2018

 No player in #AusOpen blue court history has ever led @DjokerNole two sets to love 

Can the x champion mount a comeback on @RodLaverArena? #AusOpen pic.twitter.com/OSznfOmc5U

— #AusOpen (@AustralianOpen) January 22, 2018

This man is just something else tonight... #AusOpen pic.twitter.com/7gNoUfWegw

— #AusOpen (@AustralianOpen) January 22, 2018

Wow... #AusOpen pic.twitter.com/efZ76ZjJda

— #AusOpen (@AustralianOpen) January 22, 2018

INCREDIBLE! 

Hyeon #Chung becomes the first Korean player in history - man or woman - to reach the QF at a Grand Slam.#AusOpen pic.twitter.com/R67I9fLEmn

— #AusOpen (@AustralianOpen) January 22, 2018

"When I was young I just tried to copy Novak (Djokovic) because he was my idol."

- Hyeon #Chung #AusOpen pic.twitter.com/zeyAjA6Rx0

— #AusOpen (@AustralianOpen) January 22, 2018

(Inputs from Reuters)