Top seed and world number one Rafael Nadal faces the challenge of eighth seed American Andy Roddick in his opening round-robin match at the World Tour finals at the O2 Arena in London.

NADAL WINS! Roddick battles exceptionally hard in a bid to force a last-gasp response, but Nadal holds his composure superbly to clinch the final set and a win in his opening round-robin match! Thanks for joining us.

Full credit must go to Roddick, who simply refuses to give up and fires two stupendous serves outwide to ensure that Nadal has to serve out for the match... can he do it?

Nadal holds to move to within a game of the match, and Roddick is unable to force the breakthrough with his opponent utterly unerring in his intensity and drive.

Roddick holds his serve to love in very convincing fashion, but it could all be too little, too late for the American if he is not able to break serve in either of Nadal's next two service games.

Roddick piles on the pressure to force Nadal to an extended deuce, but the Spaniard comes through unscathed to hold his serve and consolidate the break of serve in this final set. What resistance from the world number one!

BREAK! Nadal seizes the initiative in this final set with a flurry of powerful groundstrokes, and Roddick has no response as he is broken without even being able to take the game to deuce!

Nadal is imperious as he hammers two stunning forehand winners, the second of which takes him to 40-15, and that is fine play from the world number one as he levels at 2-2.

Roddick holds once more with purpose, and he struts over to his chair immediately afterwards. Nadal is very focused on clinching victory, but he will have to break A-Rod's serve again.

Nadal levels at 1-1 with real resolve and determination, and Roddick is not able to make a fast start to the set as he managed to in the first and second.

Roddick gets going swiftly with a confident, assured hold, and Nadal is not afforded a glimmer of an opportunity to launch an attack on his opponent's serve.

SET NADAL! The Spaniard wraps up the second set as Roddick fires a forehand into the net, and this match is into a deciding set now! Nadal clenches his fist in delight, and Roddick has to lift himself once more.

Nadal forces set points with a sublime forehand cross court, but Roddick refuses to give up and finds two cracking serves to narrow the deficit to 5-6!

Roddick bludgeons a stunning backhand down the line to level at 2-2, but Nadal responds in style with two superbly-crafted points to hold the ascendancy and edge closer to the set.

Nadal seizes the first mini-break as Roddick plants a backhand into the net, and the Spaniard is dictating the breaker from the outset.

Roddick somehow manages to win a tense and cagey rally to take the game to 30-15, but plants a tame backhand into the net to see Nadal peg him back to 30-30. A huge serve outwide gives the American game point, and he closes it out to take us into a tie break!

Roddick forces Nadal to 15-30 with two belligerent blows from the back of the court, but the world number one responds to take the game with two well-worked rallies to close it out. Roddick must now hold to take this second set into a tie break!

Roddick holds to love also, and both players look entirely convincing on serve as we head towards a tie-break. The American now has one last opportunity to break in this second set, with Nadal looking extremely focused at the other end.

Nadal holds to love, and that is about the most convincing, emphatic service hold you could wish for at this stage of a set. The Spaniard walks straight over to his chair, and he can now clinch the set with a break of Roddick's serve.

The number eight seed levels at 4-4, and his serve again proves too hot to handle for Nadal as he remains on terms in this second set. It looks to be heading towards a tie break now unless either player can seize the initiative.

Nadal keeps his nose in front with another composed hold, and Roddick is being thwarted everytime he looks to attack now. The Spaniard has the opportunity to launch an assault on his opponent's delivery now - can he force a second break?