1558: That's all folks. Time to sup my tea, gather my thoughts and recharge my batteries to enable my 85% effort levels of reaching somewhere near Berdo's 400%. I'd settle for 200% me thinks. See you later for Nadal vs Djokovic. Feel free to get me on Twitter for further debate and nonsense.

Rod in Manchester, via text 81111: "I am 400% committed to multi-tasking the tennis (online) and the football (TV/R5L). I can also 400% guarantee my missus will send me upstairs to the tiny TV whilst she watches The Apprentice on our bigger telly"
Winners and losers in everything eh. I'm sure your sacrifice will earn you a bigger Christmas pressie or a cooked dinner over the weekend. No?

1549: More tennis action later folks. Nadal vs Djokovic. It should be an absolute cracker. So a quick rundown of the permutations. After the the three matches, if the players are level on matches won, the positions are decided by: 1) Head-to-head 2) % of sets won 3) % of games won. So all very complicated and Berdych's win gets him right back in it in Group A. And just so you know - tomorrow's line-up for Group B sees Federer and Soderling in the afternoon. With Murray v Ferrer in the evening. Anything else you want or need to know?

1543: Tim Henman reflects on Berdych's great transformation at the end of the first set. "He was a different player. He cut out the unforced errors. He'll still fancy his chances of an upset."

1542: Berdych pays tribute to the spectators. They all do that don't they? He says: "I started this week nervously, nothing special but today went better and I started to play better and better. Just to go on court is really amazing."

1540: I didn't see that coming. Roddick was comfortable for almost all of that first set. And then his head went. Strange. What did you make of that? Tweet me, text me, get on 606.

Roddick 5-7 3-6 Berdych
The Roddick bench look on aghast (what a strange word that is) as Roddick plays a wild one long and then Berdych's back-hand down the line gives him two match points. And that's it. Roddick plays into the net. What a turnaround.

Roddick* 5-7 3-5 Berdych
Roddick's world continues to crumble as he plays a shot to the baseline, he comes into the net only to be greeted by the lineperson shouting "out". And just as a side note, I'm currently chewing on the world's worst tangerine. It's hard, tasteless and more like a a piece of wood. It's not even tangerine coloured. Not great. A double-fault and the crowd are trying to cheer Roddick up with a load of clapping. Nice touch. 40-30. A sweet rally and Berdych nicks the game as Roddick plays a limp back-hand into the net. A chance wasted.

Roddick 5-7 3-4 *Berdych
It had to happen. My 93% effort levels took a dive and I put in a 3 instead of a 4. Shocking. So all I ask is for you to do a MANUAL REFRESH and the scores will be correct. Sorry folks. My bad, as they say across the pond. A strong Roddick service game keeps him in the hunt. But the momentum still very much with Berdych.

Roddick* 5-7 2-4 Berdych
"This is Wimbledon tennis from Berdych" says Henman. 30-15 in Berdo's favour as he takes a ball on the rise before crashing it back for yet another sweet winner. Nice.

BBC 5 live at the O2: "Roddick complaining about code violation for hitting himself: "It's my racket and my foot!"

Roddick 5-7 2-3 *Berdych
Roddick loses his opening point and then complains that the electronic advertising was changing colour mid-rally. Fair point but it shows he's being rattled by things off the court which is not a good sign for his head. Berdych then blazes the ball down Roddick's back-hand and it's a stupendous winner. 15-30 and Roddick is in trouble. Official. Now definitely in trouble at 15-40 as he challenges a call that had the ball out by a foot. Crucial times. Roddick is lobbed by Berdych's defensive clearance, he steadies himself and smashes the ball back that lands out. Just. Roddick challenges it but it's out and his service is broken. Roddick returns to the chair and smashes his racquet against his trainer. Deep breaths required Andy. Andy takes a stroll onto the court and he's in the O2 shadows, pondering what he needs to do. Any advice?

Roddick* 5-7 2-2 Berdych
More naughty words from Roddick's mouth as he stutters at 30-0. He then plays it long to trail 40-0. That won't help curtail his use of the English language. And then an ace really rubs salt into the American wound.

Roddick 5-7 2-1 *Berdych
A fifth ace gets Roddick to 15-15 and despite a few glimpses of joy there for Berdo the server comes through without too much effort. Andrew Castle tells us some O2 stats - its noise is equivalent to 13 St Pauls cathedrals or two old Wembley stadiums. Or three million of my offices right now. Anybody in a noisy office? Or living room? Or street perhaps?

Roddick* 5-7 1-1 Berdych
Momentum with Berdo and he's flying at 30-0 but Roddick mixing it up and he gets a welcome point back. Roddick then can only watch the ball as the serve bounces in, and then keeps going. Game.

Roddick 5-7 1-0 *Berdych
"Roddick is definitely frustrated but he just needs to regroup now," says Henman. This is a big game for the American and he's making hard work of it at 30-30. A deft winner at the net will put a semi-smile back on his face and it's soon game as Berdych's back-hand winner-attempt drifts a few inches long. Big relief for all Roddick fans.

Roddick* 5-7 Berdych
Roddick takes the first point and the camera pans around on to the crowd. There seems to be a fair bit of hair dye in London town today. Andrew Castle is forced to apologise for a naughty word from Roddick but the American is shell-shocked. He's two points away from losing this set...and now one. That's three games in a row for Berdo and the first set. Wow. Roddick had two set points a few minutes ago and now he's blown it. He'll be fuming in that chair. Stay cool A-Rod.

Roddick 5-6 *Berdych
Roddick is cruising at 30-0 and then Berdych pulls out a crackerjack with a back-hand pass. Roddick looks utterly bemused but then gets it to 40-15 thanks to his ball dribbling downwards off the tape. His hand goes up in apology but inside he'll be giggling. But Berdych is now on it. And it's another back-hand cracker and Roddick does not even move. A-Rod then goes long and the crowd sound shocked - a game point for Berdo at last and there it is. The second serve kicks up as Berdo takes aim and his forehand is taken high and the ball lands in the corner for the winner and a crucial game. Great turnaround.

Roddick* 5-5 Berdych
Another slightly wobbly service game as the crowd begin to get a little noisy as A-Rod takes two of the first three points. "A bit of tension in the arms" suggests Henman on BBC Two. Roddick mixes it up and you sense he is feeling this is the moment. Berdych approaches the net and Roddick tries to pass him but Berdo is there... but he plays it wide. OOOfff. He won't be happy with that. Two set points. One saved as Roddick's pass just goes long. Brave Berdych still trying his 'go the net' tactics. At least he's going for it. Well played Berdo. A brilliant forehand finds the corner and Roddick struggles. Deuce. Berdych holds on though in stunning style. Roddick looks like he's got it back to deuce but Berdo bends low to pick up the ball from a half-volley and the ball loops over the net for the winner. Brilliant. It may not be 400% but Berdo has raised his game considerably.

alexwillisACE on Twitter: "Roddick & Berdych currently 2nd & 10th respectively on the ATP's no. of aces in 2010...784 for A-Rod, 530 for T-Berd"
Top stats. Thank you.

Anonymous, via text 81111: "Currently working at about 29.75% due to a combination of big lunch, lack of work, and carrying disappointment with Muzza's performance yesterday. Relying on live text to pick me up in time for the first ball tonight! Come on England!"

Roddick 5-4 *Berdych
Berdych has a great chance at 15-30 but ploughs his approach shot into the net. He stoops onto his knees and he knows it's a wasted chance. Roddick serves out the game. Plenty to think about in their chairs.

Roddick* 4-4 Berdych
Here's the wobble at the "business end" of the game. Berdo trailing 15-30. Can he hold his nerve? Ummm yes, kind of. Berdych makes it 40-30 after getting lucky with a weak swipe at the net. A final rally dictated thoroughly by both playing back-hands. The game ends with Berdo coming into the net and Roddick can't quite pull off his attempted cross-court dropshot.

bigbadbimdog on Twitter: "Did you see Doug 'the rug' Bollinger saying he'd be giving it 150,000% recently? 400% is pathetic by comparison!"
Respect is due.

Roddick 4-3 *Berdych
Forgot to mention, the head-to-head stats. Roddick leads 6-2, including having won the last four encounters, including the final in Miami and the semi-finals in Brisbane. Berdych hasn't beaten Roddick in more than two years in fact. A Berdych challenge at 30-0 but replays showed it tickled the edge of the line. 40-0. Boom. A Roddick boom that is. The American has his nose back in front.

Roddick* 3-3 Berdych
Berdych showing his class - he's ranked number six in the world. He's no donkey. A really cute dropshot from him, two more big serves and he takes his service game. Top effort. Who will crack first?

Pont in Cirencester, via text 81111: "speaking about effort I'm working at well below 100% something around 10% capacity so that I'm not too tired for the cricket tonight! Hopefully my boss isn't also watching the tennis"
See comment at 1405 for the 400% chat. Keep them coming in. What % levels are you operating on this afternoon? I'm at 92% and it's rising. The keyboard is getting hot.

edwardssport on Twitter: "I'm trying to write a final year English essay at 400%. Currently working at -400% due to the tennis"

Roddick 3-2 *Berdych
Roddick still looking comfortable and he licks his lips as he strolls into the net and crashes back a sweet winner on the back line for 30-0. Andrew Castle says on BBC Two that neither player has lost a point yet on their first serve. Interesting. Game soon over.

Roddick* 2-2 Berdych
Quick word on the fashion stakes because that's important right? Quite a conservative approach from both. Both in white - except for a few stripes - and it's the sort of outfit that was hanging around my old badminton club 20 years ago. Don't knock it. Anybody spotted any celebrities yet? Berdo fires down an ace to take the game and level. Now where are those Wednesday fireworks boys?

bbcsport_david on Twitter: "Atmos building nicely for Berd-Rodd. Rodd leads head-to-head 6-2, has won last 4 + 9 of last 10 sets. Berd in poor form.. surely a Rodd win?"

Roddick 2-1 *Berdych
More aces from Roddick and the game is rounded off nicely with a big smash straight at Berdych. The American won't be too sweaty after those opening games. He looks comfortable.
* denotes NEXT to serve

Roddick* 1-1 Berdych
Berdych has it all to do having won just eight matches since his loss in the Wimbledon final. None of the commentators are giving him a hope. Do you? Plenty of early back-hand slice being dished up by both players but this is a bit of a struggle for Berdo. Hold on though. A curling looping forehand lands on the right-hand line and gives him the game. I liked that.
* denotes NEXT to serve

Roddick 1-0 *Berdych
A comfortable start for A-Rod after losing the first point. An ace gives him the game. Steady.
* denotes NEXT to serve

1413: A-Rod opens up this match with his HUGE serve. Let's play. "Roddick will fancy this" says Tim Henman.

1411: I might not be at the O2 but I know people who are. For all gossip and latest news from the London arena then check out the tweets from our man David Ornstein or the team from BBC Radio 5 live.BBC Two have the live TV action, the live text commentary is HERE b(as you can see) or why not tune into BBC Radio 5 live sports extra. The choice is there for you.

1408: We're here again. Well I'm here in Shepherds Bush at TVC and I'd love to hear from you. Throw us your thoughts please. Anything on Murray, predictions for today or your Christmas wish-list. Anything. Tweet me @bbcsport_mark, text me on 81111 (UK) or +44 7786200666 (worldwide) with TENNIS before your message, or join the banter on 606.

1405: Berdych looks a little edgy with his pre-match interview and says: "We need to try 400% and see how it goes."
I cannot argue with the efforts amounting to 400%. The usual is 110% in sport but that is some going. I might try a couple of games of commentating this afternoon at 400% and hope my head doesn't explode. Anybody else doing anything at levels above 100% this afternoon?

1402: Following the lacklustre encounter between Murray and Federer yesterday, it's all about group A today. Nadal and Djokovic are in action tonight. But we don't care about those boys right now. Step forward this afternoon's tennis gladiators - Tomas Berdych and Andy Roddick. Both looking for their first victory at the O2 this year. Berdych, this year's Wimbledon finalist, was beaten by Noval Djokovic in straight sets in his opener. A-Rod nicked a set off Rafa Nadal before losing out in a three-set cracker. The American has the upperhand on the basis of the percentage of sets won ruling but he'll be gagging for a victory under the lights of the O2. (More on those rules in a second because it's bloomin' confusing). How do you think this one will go?

1359: It's the fourth day at the ATP World Tour Finals. Time for some tennis. Care to join me for the ride?