An ailing Novak Djokovic crashed out of the Australian Open in the fourth round as up and comer Hyeon Chung clinically took advantage of the six-time champion's elbow injury to win 7-6 (7-4) 7-5 7-6 (7-3).
The Serbian, who had also struggled with his hip in the third round, was on the back foot from the off and failed to claw back the first set before suffering further at the start of the second.
Djokovic's fighting spirit never wavered, but he could not shake off NextGen champion Chung, who was unrelenting en route to claiming the biggest scalp of his career.
Chung – the first Korean male or female to reach a grand slam quarter-final – had said prior to the match that he would "just be happy to share the court with Novak", but he was far from starstruck and an outstanding performance made him a deserved winner - albeit Djokovic, who missed six months before returning to play in Melbourne, was undoubtedly hindered by his injury.
The 21-year-old will now face another shock quarter-finalist in Tennys Sandgren on Wednesday.
Welcome to the big time Hyeon #Chung!— #AusOpen (@AustralianOpen) January 22, 2018
Our six-time champion Novak #Djokovic bows out of the #AusOpen d by the world No.58 in straight sets 7-6(4) 7-5 7-6(3) after 3hrs 21mins. pic.twitter.com/lETvt3JPJC
A series of unforced errors, including numerous double faults, allowed Chung to break Djokovic's serve twice and move 4-0 up in the first set, before the former world number one came roaring back.
Three successive games piled the pressure on Chung and errors crept into the youngster's play as he served for the set, but he battled through to the tie-break and recovered his momentum to take the set.
It was clear that Djokovic, wearing a protective sleeve on his right arm, was struggling with his elbow as he repeatedly failed to hold serve and he received treatment before the second set.
Chung held his nerve in a gruelling first game and broke the 14th seed en route to building a 3-0 lead.
As in the first set, Djokovic's fighting spirit came to the fore as he drew level, but Chung again showed great resolve and he moved two sets ahead when a stunning rally ended with the groaning 30-year-old finding the net.
A topsy-turvy third set followed, bringing the crowd to its feet as four of the first five service games were broken to leave the pair neck and neck.
Both players missed big opportunities to then take control of proceedings and a number of poorly telegraphed drop shots from the world number 58 ensured Djokovic remained in the match.
But Chung kicked off the tie-break with two superb points and, although again there was a strong response, he continued to confound Djokovic with some astounding returns to seal a huge win.
Chung bt Djokovic  7-6 (7-4) 7-5 7-6 (7-3)
Chung – 47/37
Djokovic – 36/57
Chung – 1/2
Djokovic – 2/9
BREAK POINTS WON
Chung – 6/10
Djokovic – 5/19
FIRST SERVE PERCENTAGE
Chung – 67
Djokovic – 62
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Chung – 65/47
Djokovic – 65/39
Chung – 138
Djokovic – 128
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