Korea's Chung beats Djokovic 6-7 (4-7) 5-7 6-7 (3-7)
Djokovic struggling with elbow injury in fourth-round match
World number 97 Tennys Sandgren beats fifth seed Dominic Thiem
Halep beats Osaka to reach last eight
Federer wins in straight sets
Kerber and Keys also through
Djokovic 0-3 Chung*
Image source, AFPHands up, who saw this coming? A long, long way to go, but a fantastic start for Hyeon Chung.
Novak Djokovic pulls a sloppy forehand into the tramlines, and then goes long off the backhand side from a fiery Chung first serve.
Mark Woodforde
Australian 12-time Grand Slam doubles champion on BBC Radio 5 live sports extra
Chung hasn't batted an eyelid. He has just played his game.
David Law
Radio 5 live sports extra commentator at Melbourne Park
Novak Djokovic looks nothing like a six-time champion.
Djokovic 0-3 Chung*
The six-time champion saves the first as his 21-year-old opponent goes long.
But another Djokvic serve finds the net, now the pressure is on.
The second serve is good, but Chung gets the upper hand during the rally and Djokovic cracks the net.
Another break for the young Korean.
Image source, AFP*Djokovic 0-2 Chung
When he does get one in, Djokovic finds Chung swinging like a heavyweight boxer and powering a knockout forehand down the line.
Three break points.
David Law
Radio 5 live sports extra commentator at Melbourne Park
We haven't seen the Djokovic serve looking like this this week even if it has been remodeled.
*Djokovic 0-2 Chung
Another double fault from Djokovic - I make that three in a row?! Something isn't right with that new motion...
Make that four. Djokovic needs to steady the ship, and quick - 0-30.
*Djokovic 0-2 Chung
Djokovic leaps into a backhand, moves Chung around the court and opts to lurch forward, but Chung picks his spot with the Serb rooted to the Melbourne Park floor.
Chung holds.
Djokovic 0-1 Chung*
Fantastic. Pure power and precision off the racquet of Hyeon Chung to pick out the top corner on Novak Djokovic's forehand side. But the Serb can't get near it. Deuce.
Advantage follows with a punchy serve.
Djokovic 0-1 Chung*
Djokovic has the chance to break back immediately.
Two break points to the six-time champion.
But that's a fantastic ace from Chung. One saved. Composure.
Mark Woodforde
Australian 12-time Grand Slam doubles champion on BBC Radio 5 live sports extra
When I first saw Djokovic's new serve on the eve of the tournament I thought it looked a bit of a shocker.
Then I saw it in previous round and I thought it didn't seem to be bad or obscene as I thought it was.
Djokovic 0-1 Chung*
Well, what an early opportunity for the 21-year-old. Now how can he hold up in his opening service game?
The Korean drifts forward, attempts to take a passing Djokovic forehand low at the net, but can't get enough lift on it - 15-15.
David Law
Radio 5 live sports extra commentator at Melbourne Park
What a terrible game Novak Djokovic has just played. An appalling game.
Djokovic 0-1 Chung*
That's back-to-back doubles from Novak Djokovic!
It gives Hyeon Chung the break.
Image source, AFP*Djokovic 0-0 Chung
Djokovic cracks the tape skirting the top of the net with a backhand and watches the ball trickle down his side of the court.
Double fault. Early break point chance for Chung.
Piers Newbery
BBC Sport at Melbourne Park
"New Sensation" blasts around the arena, possibly in a clever nod to NextGen champion Chung, or possibly just because they play a lot of INXS here. There isn't quite the anticipation ahead of this night session that there was for Kyrgios v Dimitrov 24 hours ago, but there is uncertainty at least. Nobody can quite peg where Djokovic stands at the moment, a title contender or just a man working his way back?
*Djokovic 0-0 Chung
Classy from Novak Djokovic, pulling Hyeon Chung one way and then the other, but the Korean sticks with the 14th seed and engages him an early rally.
Chung will challenge, but that kisses the white of the baseline - 30-15 Djokovic.
*Djokovic 0-0 Chung
Here we go.
Novak Djokovic, the six-time champion, will serve first.
Djokovic v Chung
Image source, EPASo I sat through Kyrgios v Dimitrov yesterday trying to establish which shade of bright pink it was they were sporting. We went for salmon.
No such colour clash on Rod Laver Arena today, as both Djokovic and Chung opt for white polos with navy blue shorts.
Big fan of Chung's glasses, though. Science lesson meets tennis star...
Djokovic v Chung
A word from the six-time Australian Open champion before he gets started...
"I am getting into the groove, playing better, feeling more comfortable," said Djokovic.
"One thing is to play practice sets, another is to hear the crowd, pressure, nerves kick in. I take it day by day.
"All these minor issues you have to deal with at some level."