Summary

  • 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

Live Reporting

Alex Bysouth and Matthew Henry

  1. *Djokovic 6-7 (4-7) 0-3 Chung

    What has Novak Djokovic got left in his very admirable locker? And can that elbow hold out?

    He went 4-0 down in the first set, before eventually losing it on a tie-break.

    The Serb misses a smash on the stretch, one you'd normally expect him to put away, before scooping a superb winner on the half-volley from the edge of the service box - 15-15.

  2. *Djokovic 6-7 (4-7) 0-3 Chung

    He's playing superb stuff now, the 21-year-old.

    Chung drifts into the net to meet a Djokovic backhand and deftly coaxes it into the space vacated by the Serb.

    He holds to love.

    Getty_Chung_celebratesGetty Images

  3. Chung breaks

    Djokovic 6-7 (4-7) 0-2 Chung*

    Chung looked to be desperately scrambling to stay in that point, only to leap forward and fizz a fabulous winner.

    Chung breaks.

  4. *Djokovic 6-7 (4-7) 0-1 Chung

    Long again, that was awkward, wayward, not at all comfortable from the Serb.

    Chung has two break points.

  5. *Djokovic 6-7 (4-7) 0-1 Chung

    This is magnificent. Some superb strokes from both players, as Djokovic comes out on top of a forehand exchange.

    Chung takes the next one, picking his spot right on the baseline.

    Djokovic then goes long from an aggressive Chung return - 15-30.

  6. Mark Woodforde
    Australian 12-time Grand Slam doubles champion on BBC Radio 5 live sports extra

    That was a vital game for Chung just to keep the pressure on Djokovic.

  7. Chung holds

    *Djokovic 6-7 (4-7) 0-1 Chung

    Oh, Novak. A long, looping forehand when he looked in control of the point.

    This is like exhibition stuff. Chung has the Serb sprinting and scrambling to the net, only to have to do some darting of his own to reach a precise slice.

    But he wraps up the game with a fabulous winner from deep. An important hold.

  8. Djokovic 6-7 (4-7) 0-0 Chung*

    Wow. Catch your breath if you can, the opening game of this second set has been a belter.

    Chung whips a forehand winner, only to then scuff a Djokovic passing shot around his feet.

    Another break point for the 14th seed.

  9. Djokovic 6-7 (4-7) Chung*

    Now Djokovic goes long, and he is definitely looking uncomfortable out there.

    A wayward Chung backhand lands somewhere nearer Sydney. Deuce again.

    But the Korean then pulls off an outrageous one-handed slice lob to get Djokovic scrambling, only to to see the six-time champion backpedaling and firing a winner!

    Break point.

  10. Mark Woodforde
    Australian 12-time Grand Slam doubles champion on BBC Radio 5 live sports extra

    So much must be happening in Djokovic's head at the moment.

  11. Djokovic 6-7 (4-7) Chung*

    Chung saves the first with some serious firepower off the serve.

    He scrambles right to meet a Djokovic backhand on the second break point and the Serb can only drop his return into the net.

    Deuce.

  12. Russell Fuller
    BBC tennis correspondent at Melbourne Park

    Djokovic is visibly in some discomfort. It doesn't look good for him.

  13. Djokovic 6-7 (4-7) Chung*

    Well, it doesn't appear to be troubling him early in this second set, as Djokovic cruises into a 0-30 lead with some smart groundstrokes.

    But he doesn't look too happy after a powerful Chung serves rattles his strings and drops a yard or so in front of him.

    Djokovic takes the next point to earn two break point chances.

  14. Djokovic 6-7 (4-7) Chung*

    Chung to get this second set under way.

    We just saw replays of Djokovic stretching for a backhand and then shaking his elbow with a grimace, worrying for the Serb?

  15. David Law
    Radio 5 live sports extra commentator at Melbourne Park

    I think we have a problem here. This is horrible to see.

  16. Injury problem for Djokovic

    Djokovic 6-7 (4-7) Chung

    Novak DjokovicGetty Images

    It looked like it was going to be a problem with Djokovic's foot but the six-time champion is in fact getting treatment to right elbow that ruled him out for six months.

    Not good.

  17. Mark Woodforde
    Australian 12-time Grand Slam doubles champion on BBC Radio 5 live sports extra

    You wonder how much energy Djokovic has used coming back in that set.

  18. Djokovic 6-7 (4-7) Chung

    Novak Djokovic is having some treatment on his feet between sets.

    Blisters?

  19. Game and fourth set

    Thiem 2-6 6-4 6-7 (4-7) 7-6 (9-7) Sandgren

    Unbelievable.

    What a point from Dominic Thiem. He stretches and sprints to stay in the point with Tennys Sandgren pounding the ball over the net before unleashing a huge backhand down the line.

    That takes him to set point and he wins it.

    Into a decider we go. The world number five against the world number 97.

    Thiem celebratesGetty Images

  20. Piers Newbery
    BBC Sport at Melbourne Park

    Chung was asked after his last match whether he was famous in South Korea.

    "Not sure, but I think better than last few years," he said. "In the streets, no. Tennis not that popular in Korea. But in the court, maybe someone want me to take a picture sometimes."

    Well he's certainly got a following in Melbourne now, the crowd let out a huge roar as he takes the set and they have another late-night draw on their hands. There is a mass rummage for clothing as it's a bit chilly now the sun has sunk behind the stands, and they could be in for a long evening.