Boom. Another big first serve from Berdych, this time out wide, and Kyrgios nets.

Now the Australian punches his own strings with his knuckles as he misses a passing attempt down the line. 30-0. Surely that hurts?

He is shaking his head in disappointment after another error before a big cross court forehand wins the game for Berdych.

Image source, Getty Images

Nick Kyrgios is not playing badly.

He is proving pretty formidable on his first serve as well.

Tomas Berdych does send a couple of winners away but Kyrgios keeps his nose in front in the second set.

How strong is Tomas Berdych?

This is relentless from the Czach so far. Another service hold as he batters away a wrong-footing forehand cross court. He wins the game to 15.

The home crowd are trying to get Nick Kyrgios going.

They roar their approval as Berdych nets from a big serve to level at 15-15. Better from the Australian, whipping away a heavy top spin forehand winner.

Kyrgios gets away with one there. His drop shot is reached comfortably by Berdych but, with plenty of time, he dumps a forehand into the net.

For all Djokovic's frustration, Seppi's mistakes mean he can't take advantage, as he fails to break the world number one. 

Could be heading towards another tie break in the third set. 

Image source, Gett

A sniff of a chance maybe. Tomas Berdych is wide with a backhand on the first point.

A cry of anger from Kyrgios though as he unable to control a return from a powerful first serve down the middle and an unforced error from the Australian makes it 30-15.

Two set points and Kyrgios has lost it. He launches his racket into the ground after netting - bringing some amusement to the crowd.

Brilliant from Berdych though as he stays focused and rattles away a backhand winner.

Here we go. Nick Kyrgios's politeness hasn't lasted long.

He is ranting and raving at the umpire before starting his service game. He is no stranger to a fine...

It doesn't done him any harm mind as he thunders down a few big first serves, forces some Berdych errors, and hold to 15.

Can the Czech serve the set out?

Another big ground stroke from Tomas Berdych though and Kyrgios nets. Back at deuce.

The Australian appears to have tweaked his ankle too and nets from a Berdych first serve.

The Czech survives.

Nick Kyrgios is loving Tomas Berdych at the moment. Another murmur of praise as the Czech sends another forehand whizzing past him. So much for tennis's bad boy. He is being impeccably polite.

That murmur becomes a roar though as Kyrgios jumps into a second serve return, firing a backhand winner cross court. 15-30.

Berdych is yet to lose a point on his first serve though as he makes it 30-30 but, break point, as the Czech goes long.

Break point saved - after a Kyrgios challenge - but an absolute monster of a cross court winner from the Australian sets up another break point.

Image source, Reuters

Nick Kyrgios always looks in a rush, perhaps he should slow down a little bit.

Berdych's calm, ruthless efficiency is winning the day at the moment - oh, and his thunderous ground strokes.

The Australian does hold his own in a lengthy baseline rally though, eventually forcing Berdych to net, but a cross court winner from the Czech gives him a sniff of a break at 30-30.

A Kyrgios ace eases his nerves and another unreturnable first serve finishes the game.

Image source, afp

Impressive stuff from Tomas Berdych.

The sixth seed is getting such power with his ground strokes and is coming into the net to kill points off with some solid volleying.

An ace and the Czech wins the game to love.

An angry Djokovic mumurs under his breath to himself about a missed opportunity before absolutely smashing a return virtually through the abdomen of Seppi. 

Talk about channelling your anger. Doesn't matter, though - on the next point Seppi wins the game to hold his serve. 

He's two sets up, but Djokovic is not in the best frame of mind in this third set.

Kyrgios is putting some serious top spin onto his approach shots as he comes into the net. Berdych nets and it is 15-0.

An error from the Australian and it is 15-15 and now 15-30 as a brilliant forehand winner cross court from Berdych brings gasps from the crowd.

Big power from Kyrgios to make it 30-30 but a double fault - after going for a second serve at 126mph - and break point Berdych.

He makes it. An exchange from the baseline before Berdych send a forehand winner away. First break.

Image source, Getty Images

The crowd are enjoying this.

Berdych takes a 30-0 lead with a heavy first serve that can only be hit high by Kyrgios.

The Australian takes the next point to his opponent though as, pressuring him from the net, Kyrgios watches Berdych dump a forehand into the net.

A first ace of the match though and Berdych holds.

Berdych may be 6ft 5ins but that doesn't hamper his speed around the court. He comes into the net on the back of a big return and hammers away a winner from the net.

Kyrgios is unfazed though as he rattles off the game to 15.

A promising start from both.

An early 'good shot' comment from Kyrgios as Berdych levels at 15-15 with a curling, powerful forehand winner into the corner.

Another massive forehand can't be returned by the Australian as Berdych sets his stall out early.

A good first serve and a thunderous forehand and it is 40-15. Kyrgios responds with a delightful forehand winner of his own down the line but Berdych wins the game as his opponent's miscued lob sails wide.

Image source, Getty Images

A difference in outfits.

Nick Kyrgios is wearing an orange vest, with Tomas Berdych in a more traditional green and white polo short.

Berdych to serve first.

Russell Fuller
BBC tennis correspondent in Melbourne