What's the opposite of G'day?

Urmm...Goodbye!

Make sure you come back tomorrow for more of the same. 

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We're nearing the business end of the Australian Open but we've got plenty more on offer in Wednesday's quarter-final matches.

• Angelique Kerber v Victoria Azarenka 
• Johanna Konta  v Zhang Shuai
• David Ferrer v Andy Murray
• Gaels Monfils v Milos Raonic 

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Djokovic reaches his sixth Australian Open semi-final, and it's 17-time major champion Roger Federer up next on Thursday.

 "It seems like half of my career match-ups are with him. It's always a great challenge. I have so much respect for him," said Djokovic after his quarter-final win.

Image source, .

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"Happy Australia Day everyone! Thank you for coming to tennis," says Djokovic.

Isn't he nice?

He swiftly moves on to talking about the match...

"I know Kei very well. He's not afraid to come out and be aggressive. I needed to weather the storm and I thought I did well in the important moments.

"I didn't practice yesterday. Less is more sometimes. It's like a reset button. I've played a lot of tennis in the last few weeks."

If that's Djokovic without practice...wow.

Nishikori isn't giving up just yet. His eighth ace of the match takes him to 30-0.

Ah, but he's faded again - he's been up and down like a yo-yo throughout - and Djokovic levels. 

A beautiful Nishikori volley makes it 40-30 and ace number nine means Djokovic will now serve for the match. 

We're just about to pass the two-hour mark at the Rod Laver Arena.

Nishikori comes to the net and pokes past Djokovic to make it 15-15

The Serb still has something in his locker, though - a 91mph return into the bottom corner to be precise. 

He's 40-15 up and wins his service game as Nishikori can only return into the the net.

Djokovic now a game away from the semi-finals.

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Nishikori smacks a sublime winner down his right-hand side and goes 40-15 up.

But as soon as Djokovic makes it 40-30, Nishikori's negative body language reappears - shoulders down, grumpy face.

A fabulous, fabulous rally now...Djokovic slices into the corner and Nishikori returns but it's just out. 

We get to our third deuce of the game, as the two continue to battle hard. 

Advantage Djokovic...second serve Nishikori...and Djokovic snatches the point.

Djokovic is back on serve and quickly takes a 30-0 lead.

But Nishikori returns well cross-court and it sneaks in. 30-15. 

The pair send each other back and forth across the back of the blue floor, and eventually Djokovic holds out to keep his serve.

Is Nishikori limping slightly? Looks that way.

Djokovic is giving Nishikori a taste of his own medicine.

The Serb takes a 0-40 lead, with Nishikori's forehand going past the baseline for the umpteenth time.

Djokovic breaks again. Anyone fancy winning their own service game?

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Nishikori has a huge bandage on his right leg. The 26-year-old doesn't look comfortable at all but he's back out on court.

And he wins the first two points on Djokovic's serve!

Make that three. It's 0-40 after a powerful forehand into the bottom corner of the court. 

He's broken Djokovic to love! Is that a magic bandage he's put on?

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Nishikori's drop shot lets him down again and Djokovic leads 15-30.

Oh dear, the racquet's on the floor now. Nishikori is having a strop. 

Djokovic has two break points...and the Japanese hits his return into the net.

Just when he thought he was getting somewhere....

It's not been vintage Djokovic today, if I'm honest.

The Serb hits a light return into the net to make it 15-15.

And then as he gets right into the net he tries to gently tap it over...but it's short. His coach Boris Becker lets out a weary sigh in the stands.

Break point Nishikori now, but a faithful Djokovic ace brings it back to deuce.

Bang! At last! Nishikori breaks the world number one as the Serb hits a return too low. Game on?

Can anyone else out there say they've helped stretch out a world number one?

Well, one of the Australian Open ball-boys can. Djokovic used a little on-court helper to pull his arms back in preparation for the third set. 

It's helped by the looks of it. Djokovic has another break point. 

A shocking miss as he tries to hit cross-court and the advantage returns to Nishikori. The Japanese hits an ace to win it. 

Image source, Reuters

Nishikori has twice come back from two sets down to win a match...but can he do it against the world number one?

If he does, he will become the only the second Japanese man to reach the semi-finals of the Australian Open. 

Jiro Satoh reached the last four at this tournament in 1932.

Remember that far back? Thought not.

It's set point to Djokovic.

A strong, strong serve from the Serb and Nishikori has no chance of returning. 

Now the Japanese has a mountain to climb to get back in this contest.