A finger point from Hyeon Chung, a hint of celebration for the first time after he draws Novak Djokovic in and out like the hokey-cokey before slicing a volleyed winner.

The Korean then takes on a forehand volley from mid-court to hold.

Hyeon Chung has lost the last three games after winning the first four. He needs to hold serve.

A little tentative from the Korean, until he steps into a short Djokovic forehand and whips it across court to level at 15-15.

Djokovic is struggling to keep up with Chung's strokes to his forehand side, and as the 21-year-old leaps into a backhand the six-time champion can only flop it low into the bottom of the net.

Piers Newbery
BBC Sport at Melbourne Park

A lot of players insist on their support team standing and applauding their every winner, but Team Djokovic has been around the block a few times.

Andre Agassi and Radek Stepanek are so far sticking with the hunched-forward-while-clapping pose for the most part, saving their knees for battles to come. They've even laid out towels for their elbows.

They do haul themselves up after that lengthy Djokovic hold and spend the changeover staring in their man's direction. It's a strange way to earn a living.

Image source, Reuters

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

It was a different Djokovic in that game. He was at the net a few times - a change of pattern from the previous games.

What hasn't changed is the serve. He is still struggling to find the consistency.

Novak Djokovic is looking a lot more mobile. He scurries forward, gets Chung on the run and then smashes home with an overhead volley.

You could feel the early frustration oozing out of the six-time champion there...

He makes an important hold.

Nice from Hyeon Chung, using his eyes and wrong-footing Novak Djokovic in centre court with a powerful backhand winner.

Djokovic claws his way back to advantage, but Chung digs deep into his arsenal and picks out another superb backhand winner down the line.

Lovely stuff. Deuce.

Novak Djokovic appears to have slipped into gear on his serve now, despite that double fault, he's connecting with more ferocity and dictates a point that sees Hyeon Chung sprinting towards the net to reach a drop shot, only to prod it wide.

As soon as I praise the Serb's serve, another double fault... SIX for the first set already. Deuce.

Hyeon Chung has some serious fizz in that forehand, but he can't wrap it around a speedy serve down the T from Novak Djokovic.

The Serb challenges what he feels is an ace, but it's wide, and he then double faults.

Michael Rose: I can't remember the last time Djokovic starting a match as badly as this.

He takes it! At the fifth attempt. That was a big game in the course of this match, you feel...

And now it's Hyeon Chung with the advantage, Novak Djokovic flopping an unorthodox forehand well wide - he looked a little uncomfortable there?

Chung just can't polish this game off at the minute, though. Djokovic is hanging in there, and gets a fifth break point when the Korean loops a forehand long.

Another break point for the six-time champion as Chung overcooks a groundstroke from deep.

Djokovic has him on the run, the Korean sliding into a defensive forehand slice, but the Serb then cracks a forehand long.

Deuce, again.

Image source, AFP

Advantage Chung. A big serve when he really needed it, nearly knocking the Serb off his feet.

This is the second time Chung has recovered from 0-30 in this match already... but Djokovic scrambles back to deuce.

Chung saves the first one with a spinning, rising serve that has Djokovic at full stretch.

The Serb goes long with a backhand from the baseline for the second.

One more to find a way back into this first set.

Nope. That's long, in almost identical fashion. Deuce.

Image source, AFP

Double fault. Three break points Djokovic.

We've reached the 20-minute mark, probably the best 20 minutes of Hyeon Chung's young career so far - no doubt up there with the worst of Novak Djokovic's...

Chung dips into a backhand to rifle it narrowly above the tape, but Djokovic is beginning to warm up and dashes into a short ball with a punishing forehand winner.

Chung goes long with a loose backhand - 0-30.

Fifth seed Dominic Thiem is in big trouble. He's just lost the third set on a tie-break against the world number 97 Tennys Sandgren.

Thiem is going to have to go the distance now or he is out.

Could two upsets be on the cards tonight?

Image source, Getty Images

Image source, Reuters

That's better from Novak Djokovic, catching the line right in the top corner and sailing into a 40-0 lead on serve.

He holds to get on the board.

David Law
Radio 5 live sports extra commentator at Melbourne Park

Djokovic looks embarrassed with the way he has started.

Nice, sliced second serve from Hyeon Chung, but it's returned with interest from Novak Djokovic and that forces the 21-year-old to go long.

Oh dear. A whole lot of frame from the Serb who mistimes a forehand and loops it high into the Melbourne Park sky.

Another wayward one that gets nowhere near the sweet spot sees Chung hold.