Third seed Novak Djokovic takes on Czech Tomas Berdych in their round-robin stage clash at the World Tour finals at the O2 Arena in London.

DJOKOVIC WINS! The Serb races to 30-15 with two fierce forehands, then Berdych puts a backhand into the net tamely to hand his opponent two match points. The Czech finds a brilliant backhand lob to thwart Djokovic with the first, but the Serb clinches victory with a fine first serve - what a performance!

The Serb is presented with a glorious opportunity to pile on the pressure with a smash into an open court, but he inexplicably fires it wide, and Berdych moves to 30-0. Djokovic manages to locate the baseline with a fine forehand winner, but the Czech holds firm to force the Serb to serve out for the match.

Djokovic assumes a 30-15 lead with a crisp backhand winner down the line, but he then plants a sloppy backhand into the net as Berdych gets back to 30-30. The Serb eventually holds to edge closer to sealing victory with two fine first serves.

Berdych is able to hold with considerably more confidence and comfort as Djokovic takes his foot off the pedal slightly, and the Czech again ensures that his opponent has to continue holding to preserve his advantage.

Djokovic restores his three-game cushion in this second set, and the Serb is looking incredibly confident now as he holds serve to 15 and throws the ball away. This is a performance of the optimum efficiency from the third seed.

Berdych gets himself on the board with a solid hold to 15, and he closes out the game with a sublime drop shot which completely deceives Djokovic. The deficit is reduced, but the Serb still has the upper hand.

This is one-way traffic at the O2 Arena, and Djokovic opens up a 3-0 lead in this second set with Berdych not able to muster a reply after having been broken in the previous game. The Serb is flying!

Berdych is immediately put under immense pressure on serve, and Djokovic forces the break from 30-40 with the Czech unable to find a big serve to bail himself out! The Serb stamps his authority on the second set from the off!

Djokovic holds with ease to open up the second set, and the Serb is looking pretty imperious today as he continues to find a good rhythm on serve with Berdych unable to muster a tangible response.

SET DJOKOVIC! The Serb wraps up the opening set in clinical fashion as Berdych wavers yet again on serve and is ruthlessly punished! Djokovic fires a forehand down the line to force his opponent to plant a tame backhand into the net, and that closes out the set!

The Serb moves to within a game of the opening set with a confident hold, but Berdych still manages to really test his opponent with a string of powerful ground strokes. Can he now force Djokovic to serve out for the set?

Berdych ensures that Djokovic has to keep his nerve on serve as he holds to love, and that was a stunning game from the Czech, who finds three huge serves and moves in court to back each up.

Djokovic is unerring in holding once more with aplomb, and the Serb finds a fantastic rhythm on serve as he edges closer to taking the opening set. Berdych now has the pressure on to hold.

Berdych reduces the deficit with a solid hold, and Djokovic's relentless pressure is not enough to challenge the Czech on this occasion. The sixth seed is battling exceptionally hard, but can he get back on terms now?

That's much more simple for Djokovic, who finds three fierce first serves to keep his opponent pegged back firmly behind the baseline to hold comfortably. Berdych is not able to force the initiative in the game whatsoever.

Djokovic pounds two belligerent forehands down the line to peg his opponent back to 0-30, but Berdych responds superbly to take the game to deuce. Djokovic wins a 24-stroke rally to post a break point, but the Czech holds his composure to close out another mammoth game and get on the board.

Djokovic consolidates his break of serve, but only after an epic game which sees the Serb come through an extended deuce with Berdych throwing everything at his opponent in a desperate bid to break, but to no avail. What a game that was!

BREAK! What a stunning start from Djokovic, and what a sluggish start from his opponent! Berdych can only find two first serves, and the Serb pummels three glorious forehand winners to seal an emphatic early break!

Berdych wins the toss and elects to serve first, and the big sixth seed will be desperate to get off to a solid start.

This pair have met four times previously on the ATP Tour, with the Serb prevailing on three occasions: in Bangkok, Miami, and the Davis Cup this year. Berdych's solitary win was quite a significant one: the semi-finals of Wimbledon this season.