So tomorrow's singles slate looks like this:

14:00 GMT: Rafael Nadal v David Ferrer

20:00 GMT Andy Murray v Stan Wawrinka

That latter match is a straight shoot-out for a semi-final spot against Roger Federer.

We'll be here. I'll hope you will too...

Novak Djokovic - gentleman and scholar.

After offering gracious words on court he heads to the wings to scribble his name on a gaggle of balls and pose of selfies with his fans.

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Novak Djokovic on the prospect of playing Rafael Nadal in the semi-finals: "He has another match tomorrow and I will watch that with my team to try and prepare. We have played so many times - I think a couple of times on this very court. 

"He has played great in his first couple of matches in London and hopefully I will be able to play my best. That is what is needed to beat him."

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Tomas Berdych trudges off the O2 stage on the back of three successive defeats at the World Tour Finals.

He will hope to kick on next season under coach Dani Vallverdu.

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And Novak Djokovic is back on the winning wagon. After his defeat by Roger Federer on Tuesday, he has put Tomas Berdych to the sword.

Berdych takes the game's first point but nothing more.

Djokovic always had his number.

Novak Djokovic suddenly jimmys the lock on the Tomas Berdych serve.

Love 40 as he gets busy on return. Only another slice of Lady Luck delays Berdych's demise in the game as a net cord breaks his way.

Berdych is all apologies.

Djokovic ignores his palm of peace and slaps away a return winner on the next rally.

He serves for the match next.

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Gigi Salmon
BBC Radio 5 live sports extra commentator

Djokovic skips to the back of the court. Both players take their towels. We had the tantalising 10th game. Is this the enormous 11th?

Novak Djokovic drops one point on his way to the game. His game feels like it is sharpening up nicely as he comes to the pointy end of things though.

The world number one finds a delicious angle for the final winner from behind the baseline and bang centre of the court.

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Tomas Berdych makes it to 40-0 via a chunky net cord and a whippy ace down the middle.

Another dose of pure service speed delivers the game.

Novak Djokovic chalks up another service game in unremarkable style.

There is a distinct lack of fizzle in the O2 at the moment. There is more atmosphere in deep space.

Image source, Reuters

Tomas Berdych's mix of serving speed and big forehand, with a unhealthy dash of errors thrown in, is good enough to hold off an indifferent Novak Djokovic once more.

This set feels like a flabby recent spy blockbuster that could be half an hour shorter. 

Let's cut to the finale.

Novak Djokovic, with his semi-final spot secured with the first set, is still on auto-pilot.

His groundstrokes lack his usual venom and intent and he is made to fight through from deuce once again.

Is he coming off the boil after a long season? Or is he still the man to beat this weekend?

Tomas Berdych picking up steam and scooping up a third game in succession.

Mid-set momentum is one thing though, doing it at the business end is what matters.

And no-one operates better in that zone than Novak Djokovic.

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Boom! And Tomas Berdych is back in room!

The Czech had looked like he was sleep-walking towards the O2 exit, but a wallop of a forehand down the line converts a break point at 30-40.

Is there still a twist in this tale?

Tomas Berdych steadies the ship with a spitter of a serve out wide. 

A little toe-hold in the second set? He needs to dig in deep and hard to swing the momentum back his way.

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Rolling Djok. The Novak Djokovic express is chugging for home.

Another game disappears down the gurgler for Tomas Berdych and the spotlight swings back on his own serve.

Berdych broke back from a break down in the first set. A double break would surely too much of a gap to bridge in the second.

Novak Djokovic is playing as though he wants to get back in time for last orders at the players' base at the Savoy hotel.

He brings up 0-40 to put Berdych in a very tight little corner.

The Czech makes a decent fist of it, but sabotages his own comeback attempt as he double-faults pushing his luck at 40-30.

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Stick the reserved sign down on that semi-final spot.

Novak Djokovic will play Rafael Nadal in the last four on Saturday as he closes out the opener.

Even if Berdych wins the match, the Czech is heading home for the year.

Tomas Berdych lamps a forehand at 30-15 up. It comes off the strings clean, but lands apparently a little dirty and is called out by the linesperson.

It looked marginal in real time. Berdych opts not to invoke the video gods. Shame, because on the virtual replay it looks plain wrong with the ball snicking the paint.

What could be 40-15 is 30-30 instead.

Deuce. Berdych unwraps a bullwhip of an ace down the middle to see off the danger.

But Djokovic clinches a second as Berdych touch at the net goes AWOL.

That decision not to challenge looks costly. Djokovic to serve for the set and his semi-final spot next.

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Tomas Berdych is raiding the net like an unmanned tuck shop at the end of term.

Another dart into front court catches Novak Djokovic by surprise and punishes the Serb's nothing-much slice.

Djokovic is short of the full ticket as well - lacking his usual zip and fire. Deuce.

The favourite makes it over the line, but he is being made to think and run hard out there.