Six-time champion Novak Djokovic and top seed Rafael Nadal are both are out of the Australian Open tennis tournament after each losing their quarterfinal.

Novak Djokovic (L) of Serbia congratulates Chung Hyeon of South Korea after Chung won their match at the Australian Open, Melbourne, January 22, 2018.
Novak Djokovic (L) of Serbia congratulates Chung Hyeon of South Korea after Chung won their match at the Australian Open, Melbourne, January 22, 2018. (Reuters)

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.

Djokovic, grimacing occasionally and flexing his elbow, dropped the opening four games and although he clawed back the deficit 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.

Again Djokovic battled back from a break down in the third set to force a tiebreak but Chung refused to let the 30-year-old Serb off the hook.

Chung hooked 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 into the tramlines.

Chung will face unseeded American Tennys Sandgren for a place in the semi-finals.

Spain's Rafael Nadal after retiring injured during his match against Croatia's Marin Cilic at the Australian Open, Melbourne, Australia, January 23, 2018.
Spain's Rafael Nadal after retiring injured during his match against Croatia's Marin Cilic at the Australian Open, Melbourne, Australia, January 23, 2018. (Reuters)

'Rafa' out injured

An injured and visibly struggling Rafael Nadal retired while trailing in the fifth set of his quarterfinal match against Marin Cilic of Croatia.

The top-ranked Spaniard saved five break points in the last game before Cilic broke his serve. Nadal then conceded the match.

Sixth-seeded Cilic advanced with a score of 3-6, 6-3, 6-7 (5), 6-2, 2-0, retired.

Cilic in his semifinal faces Briton and world No. 49 Kyle Edmund, who earlier beat Bulgarian Grigor Dimitrov in four sets.

It was only the second time Nadal had retired during a Grand Slam match  — the last time was also an Australian Open quarterfinal, in 2010 against Britain's Andy Murray.

On Tuesday night, he needed a medical timeout after going down 4-1 in the fourth set, getting treatment on his upper right leg and hip.

He returned but was clearly bothered by the injury, limping and trying to stretch between points.

After being broken to fall behind 2-0 in the fifth, Nadal called it quits, and shook hands ruefully with the chair umpire and Cilic.

Cilic had only previously beaten Nadal once in their six previous matches, in their first match in 2009.

Source: Reuters