So what does that mean? Well it means that Djokovic is not guaranted a place in the semis, as if he loses to Berdych it will come down to games won. These round-robins are a touch confusing aren't they? Let me know what you think on Twitter @Reda_Eurosport. Thanks for joining me, I'll be back tomorrow for the Group B matches, with Federer facing Ferrer and Del Potro up against Tipsarevic. Cheers.
TSONGA 5-7 6-3 1-6 - GAME SET AND MATCH BERDYCH! Two breaks up and Berdych can afford to take a few risks, but he leaves the left baseline unguarded as Tsonga passes nicely away. But Berdych opens up a nice, crisp forehand beyond Tsonga's lunge, and a monster serve down the middle is followed by a poor, long backhand by Tsonga and we have two match points. Berdych takes them with a dipping forehand winner to the left, wrapped up in 1h52.
TSONGA 5-7 6-3 1-5 - BREAK! I hope Tsonga hasn't just given up, Berdych is all over him now as a fierce forehand cross lands beyond the Frenchman's stretch. Three break points, on second serve now, and Tsonga rushes to net to slice his backhand wide and leave Berdych serving for the match.
TSONGA 5-7 6-3 1-4 - Tsonga drills a ferocious double-backhand away from Berdych to start his comeback in earnest. The Czech brings out his power serves to edge ahead but his first double fault tonight draws them level at 30-30. And he holds to back up his break - if he wins here it's all open for qualification. Very interesting.
TSONGA 5-7 6-3 1-3 - BREAK! Hello, Berdych now has two break points, and he takes them as Tsonga overhits a forehand cross beyond the right baseline. Deary me, he's put himself in real trouble and it's his own fault!
TSONGA 5-7 6-3 1-2 - Berdych holds in about as much time as it takes to say "Celtic have just beaten Barcelona, having almost beaten them last time". The rest is a footnote I fear.
TSONGA 5-7 6-3 1-1 - Tsonga edges 9-8 ahead in the ACE count and holds to 15 with a cool diagonal forehand off the line.
TSONGA 5-7 6-3 0-1 - Break points Tsonga early in the third and final set but he stumbles to send an overhead long, and a fine serve levels at deuce. He's made to work for it but Berdych finally holds to start the decider. Tsonga looks annoyed with himself, he sensed a real chance.
TSONGA 5-7 6-3 - SET! And a wonderful selection of volleys at the net see Tsonga roar back to set point, one flying backhand and a cool pass. Classic JWT. ACE to hold under serious pressure and force a decider. Suddenly Tsonga shows magnificent form.
TSONGA 5-7 5-3 - Tsonga is suddenly in trouble as he serves for the set, 0-30 down after some poor deliveries are exploited by Berdych, but he's back in it as the Czech returns long. Massive serve to follow, Berd gets something on it but Tsonga adjusts his body to curve a forehand down the line. 30-30. But break point now as Tsonga goes wide! But saved with a majestic second serve ace down the middle! Ballsy from Tsonga!! Deuce.
TSONGA 5-7 5-3 - Good show from Berdych as he quickly turns that service game around, still no double faults in this match as Tsonga leads the winners count 19-10.
TSONGA 5-7 5-2 - Tsonga is holding it together on serve though as he takes the next one to 15 with Berdych netting then going long from deep. Berdych serving to stay in the second.
TSONGA 5-7 4-2 - Big Berd stops the rot with a comfortable hold as he unleashes his power on Tsonga, a big hitter himself, on serve. The Frenchman still a break up.
TSONGA 5-7 4-1 - Lovely volley at the net, and a wicked serve brings up 40-15 for Tsonga, who holds as Berdych slips while returning.
Obviously that Tweet game moments before Berdych was broken, but you get the point. The indoor arena suits his beefy power game.
@joeldf: "Berdych adding coolness under pressure to his powerful groundies." - agreed. He still has minor issues on the big points, but he's matured into a big hitter with benefits.
TSONGA 5-7 3-1 - BREAK! Berdych fails to take the game point off deuce as he again allows Tsonga to make it a moving point, the Frenchman using all the angles before pinging it away. And now he has another break point, taken as Berdych's follow-up lands long. This one's a keeper!
TSONGA 5-7 2-1 - An official review of a Tsonga effort shows it was wide, but he levels and now has two break points as he constructs a running point that suits him far better than Berdych, who angles a backhand across the net but wide. Can he take them? Not at the first time of asking, as a brutal serve is somehow returned but only for Berdych to crack it away down the left. Still one break point, but lost as Tsonga returns long, deuce.
TSONGA 5-7 2-1 - Berdych has a sniff at 0-15 but Tsonga is a touch more composed all of a sudden and shows good variety on his groundstrokes to move 40-15 as the Czech nets a diagonal forehand. But Tsonga mis-hits a backhand to net and shows his frustration. He channels it well enough and holds to 30.
TSONGA 5-7 1-1 - Berych launches some more of his ferocious bullets at Tsonga to hold in quick time. Mimicing the first set this - any error will prove vital.
TSONGA 5-7 1-0 - Love hold for Tsonga to open this second set. He's been somewhat inconsistent close season and it shows.
TSONGA 5-7 - SET! No trouble for Berdych as he holds to claim the first set, battering Tsonga with his angled deliveries, although the Frenchman did pull one back with a majestic return that spun away off the left baseline. Chapeau, but no cigar as an ACE down the middle closes it out to 15.
TSONGA 5-6 - BREAK! Berdych leaps for joy as he moves 30-15, and the Tsonga seems to go wide for two break points - he challenges, but it was wide, and Berdych breaks thanks to another miss from the Frenchman, whose forehand pass down the line is well wide. Berdych is serving for the set!!
TSONGA 5-5 - Berdych responds by blasting his way to 40-0, although Tsonga pulls one back with a stretching pass that swings outwards beyond the lunge of the big Czech. Tsonga's next return off second serve is weakly spanked to the net as he tried to open up a flat forehand winner, and it's another hold of serve.
TSONGA 5-4 - Almost a marvellous winner down the line from Berdych, but it lands inches wide. 40-15 Tsonga, and he holds with an identikit pass that lands a few inches in this time and Berdych is serving to stay in a set that has been too close to call, although Tsonga has hit 12 winners to 7.
TSONGA 4-4 - Now a spot of bother for Berdych, who pulls back to 15-30, but a wild backhand from Tsonga lands well off court. Berdych takes the opportunity to crank up the power, and a forehand winner towards the right baseline catches Tsonga off-balance and he spins it well wide.
TSONGA 4-3 - Tsonga is in trouble again, another break point down and on second serve after putting one wide... Berdych should have him here as Tsonga is stranded, but he volleys long! He challenges, but it was out and we're back to deuce. Error from the Czech, that was a real chance. A fine forehand pass brings up game point Tsonga and he holds as Berdych nets a backhand return. A big, big hold.
TSONGA 3-3 - The Frenchman is 0-30 down suddenly but aces his way back into it, before putting another forehand weakly into the net. Two break points Berdych! The first is saved with a powerful serve and rush to net, rounded off with a diagonal forehand beyond the Czech, before the trusty serve brings it to deuce. They trade blows off 40 for a few points, one backhand slice across net a delight for Berdych, and this could be a crucial game.
TSONGA 3-3 - Boom boom boom, the big Berd bombs 30-0 up but the next point is a baseline slice affair that Tsonga shades as Berdych clips one wide. The first point against serve in a while. And now we have 30-30 as Tsonga pings a flat, zippy backhand winner down the line after working the forehand. But he puts one wide and Berdych holds off 30 to continue the pattern.
TSONGA 3-2 - Tsonga responds in kind with his own hold to zero, both men serving well enough to construct and dominate their points. These are quick games - three minutes each on average - so I expect at least one tie-break.
TSONGA 2-2 - Better from Berdych, who cruises to a dominant hold as Tsonga leans into a long forehand return. Game to love.
TSONGA 2-1 - All fairly predictable stuff so far as Tsonga holds with relative comfort. Lots of power from Berdych, and some effortless movement from Tsonga as he dictates the tempo of the points.
TSONGA 1-1 - When Berych comes to net it can be quite intimiating, but Tsonga keeps his cool to flick an angled backhand clear of the approaching Czech. But, after dictating the next point with some dipping groundstrokes, Tsonga nets one and it's level. Berdych ups the power to ease ahead though, and he holds to 15 as Tsonga flips a forehand low into the net after some good crosses from the Czech.
TSONGA 1-0 - Tsonga holds to 15 as he patiently strikes the ball with good length from deep, Berdych going long from a lengthy rally and then a return. Decent start for the Frenchman.
Okay so they're done hitting and we should be underway in the next few minutes. If Tsonga wins, remember, Djokovic is through.
More good news for British tennis fans - Jonny Marray just loves playing doubles in London, as the Wimbledon champion and his Danish partner have beaten the Mirnyi-Nestor partnership to move into the semi-finals. Well done lads! That means the singles should get underway in 20 minutes or so.
HEAD-TO-HEAD: Berdych leads 3-1 on this, winning their last two encounters in the final at Stockholm and the quarters in Shanghai, both this season. But Tsonga won here in the semis last year, and he seems to get excited in London - although you wouldn't have known against Djokovic the other day. Another one that's too close to call, can see it going all the way again.
My name is Reda Maher and I'm your man on the ground at the O2, bringing you live updates and reports from all the singles clashes. Any pre-match predicitons or in-play chat around this or any of the other matches, or indeed this event in general, feel free to Tweet me @Reda_Eurosport.
Hello and welcome to our LIVE coverage of the ATP World Tour Finals Group A clash between Jo-Wilfried Tsonga, the seventh seed from France, and fifth seed Tomas Berdych from Czech Republic. The preceding doubles match has gone to a Champions tie-break, so this will likely start at around 8pm.