So, we're two and half days in and I think it's fair to say that this tournament hasn't really come to life. Let's hope Novak Djokovic and Stan Wawrinka can change all that tonight. Join us at 1945 for live text and radio coverage of the world number one against the Aussie Open champion. Catch you then.
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Tim Henman
Former British number one on BBC Two
"That's two very disappointing matches for Cilic. He is 6 ft 6 ins with a big serve and he has lost four sets and only won six games. He's just not doing the basics right and he won't be a happy man."
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The match stats don't make pretty reading for Cilic. He only won 61% of points on his first serve and 41% on second, compares with his opponent's 71% and 70%. His serve was broken four times in two sets and he only won 43 out of 106 points.
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Nice line Tomas. That match lasted 74 minutes. Berdych is now 0-5 in opening matches in the World Tour Finals and 5-0 in second matches.
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Tomas Berdych: "I was really trying to focus on my tennis and my game, trying to go point by point. I think today was more fighting and getting through. It's good to have a win and it always counts.
"It's not my first year. I have the experience of losing the first match in the past and I know how to come back. I think that was the biggest difference today.
Asked about facing Djokovic next, Berdych asks the crowd "Any tips? I will need some. I just want to try to bring my best tennis and we'll see what happens. I hope I can have a great match."
Game, set and match Berdych
Berdych 6-3 6-1 Cilic
Talk of an early bath here, but have we spoken too soon? Berdych pushes a forehand into the tramlines to give Cilic a break point but snuffs it out with ace number five. Another one is saves, but two points later we're at match point. And the contest ends, somewhat fittingly, with a Cilic backhand into the net.
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*Berdych 6-3 5-1 Cilic
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Cilic is officially his own worst enemy. A dreadful drop shot and a powerpuff approach earns Berdych three virtual match points. Cilic saves one with possibly his best shot of the match, but cannot sustain that level and nets to leave Berdych on the brink.
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Berdych 6-3 4-1 Cilic*
From 30-30, Cilic fails to get a ball back into play and Berdych is closing in on the match now. Goran Ivanesevic has had enough. He looks like a father whose son has just been sent off for diving in an under-11s match.
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David Law
BBC Radio 5 live sports extra commentator
"This is wild tennis at the moment for Marin Cilic - he is all over the place at the moment. This must be a nightmare if you are a professional athlete, surrounded by this sort of crowd, and it is just not working - you must want the ground to swallow you up.
"You can see the irritation and strain in his features after every point. Yet there's a calmness and serenity about Berdych."
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Andrew Mark Spence: "Despite this performance in this match, I see Cilic winning a second Slam in '15...possibly Wimbledon."
Sam Hedge: "London should permanently host this event. The O2 arena has a unique atmosphere."
James Donald: "Both of these players are trying to hit themselves into form. Expecting to see a lot of unforced errors but also some huge shots."
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*Berdych 6-3 3-1 Cilic
Cilic certainly has plenty of fans in the O2, judging by the number of Croatia football shirts in the crowd. But can he give them something to cheer about? Berdych plays a superb point to level up at 30-30, then lands a backhand right on the line to gain a break point. Another horrible rushed backhand from Cilic gives Berdych the game.
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Berdych 6-3 2-1 Cilic*
Thank goodness Tim Henman and Andrew Castle have healthy heads of hair because they are tearing it out in exasperation over Cilic's performance here. He opens up two break points but slops a second serve return into the net. Berdych gets back to deuce, and puts the game away thanks to another backhand howler from Cilic.
Get involved
John McEnerney: This may go the distance once MC finds his rhythm both big hitters plus Goran is there in MC's corner! Please 3 sets lads!
Andrew Mark Spence: "Despite this performance in this match, I see Cilic winning a second Slam in '15...possibly Wimbledon."
Sam Hedge: "London should permanently host this event. The O2 arena has a unique atmosphere."
James Donald: "Both of these players are trying to hit themselves into form. Expecting to see a lot of unforced errors but also some huge shots."
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*Berdych 6-3 1-1 Cilic
Cilic just can't find any consistency out there. from 40-0 he lets Berdych back in the game with a couple of unforced errors, but stumbles over the line when the Czech nets a backhand. Coach Goran nods approvingly.
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Tim Henman
former British number one on BBC Two
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"Berdych did a good job in the first set. He kept his first serve percentage high and moved forward when he got the chance. He'll be looking for more of the same. Whereas Cilic has to cut those unforced errors out and look to get on the offensive in these points when he's facing the serve."
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Berdych 6-3 1-0 Cilic*
Berdych is riding the wave now, hitting the spot with his serves and keeping his opponent guessing. He holds to 15 with a fizzer tot he corner that wrong-foots the big Croat.
Rise of the super coaches
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The debate around who Tomas Berdych will bring in to his coaching set-up intensified after his first round battering.
The Czech said he wants to add somebody with a "new and different experience" - his current coach Tomas Krupa, who spent two months inside the top 300 in late 1995, helped Berdych to the Wimbledon Final in 2010.
BBC commentator Andrew Castle wonders if that would be "hard to take" for Krupa, while former British number one Tim Henman says: "It is an interesting concept that has really come into the game in the last few years - talk of these 'super coaches'.
"We thought it might be [eight times Grand Slam singles title winner] Ivan Lendl, but he said no. It will be intriguing to see who it is."
Game and first set Berdych
*Berdych 6-3 Cilic
Berdych doesn't waste any time in snaffling his opportunity. Two set points: the first is missed, the second taken when a Cilic forehand misses the line by a hair's breadth. 1-0 to the Czech.
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Berdych 5-3 Cilic*
Hold on, is this the Cilic charge? A heavily top-spun approach and a brutal overhead give him an opening at 0-30 on the Berdych serve. Then another dart to the net and a backhand volley sets up two break points. Berdych saves the first with a brilliant backhand winner and the second when Cilic lets himself down with a loopy drive past the baseline. There's no second chance for Cilic as Berdych moves to within one game of the set.
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Tim Henman
former British number one on BBC Two
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"There's been 44 points but only six winners - that's 38 points ending in either an error or a forced error. I'm not suggesting they keep the ball in the middle of court and don't miss, but when there's that many mistakes you've got to be aware of it. They've got to get rid of them."
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*Berdych 4-3 Cilic
Cilic is having to work like a dog just to win a point. He slips to 15-40 down, but fights back to win the game with some booming serves and a drilled crosscourt backhand.
Bowl half full
Piers Newbery
BBC Sport at the O2 Arena in London
"This match looked like being the hardest sell of the week and not surprisingly, the upper bowl is probably only half full. Spaces in the lower bowl are far fewer, however, and it's a mark of the success of this event that a relatively low-key contest like this can attract well over 10,000 spectators paying top whack on a weekday afternoon."
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Berdych 4-2 Cilic*
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The rallies are getting longer. The quality higher. But still Berdych is looking the likelier to run away with the spoils. He holds to love when Cilic goes long. Too long.
His coach Goran Ivanesevic looks a bit anxious in the crowd. Goran reached the semi-finals of this tournament three times.
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*Berdych 3-2 Cilic
Cilic so far looks a shadow of the player who stunned everyone to win his maiden Grand Slam title at Flushing Meadows. For every big serve and crunching groundstroke there's an elementary mistake. Luckily the pros outweigh the cons in this game and the Croat stays in touch.
"Marin Cilic said in his interview after this last match that he was shanking a lot of shots, and there's already been a few out there today. It's nice to see that even some of these big names still make rookie mistakes."
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Berdych 3-1 Cilic*
Both players are gaining plenty from their second serves and Cilic can't contend with a couple of big kickers from Berdych. The Czech puts the game to bed with an easy smash.
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*Berdych 2-1 Cilic
Good signs from the 6ft 6ins Cilic. There's much more power and purpose about his serve and ground-strokes here as he comfortably holds to love.
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Berdych 2-0 Cilic*
Berdych, 29, reached the semi-finals of the ATP Tour finals in 2011. Cilic is making his debut at the tournament. And it's turning out to be a pretty miserable debut so far as Berdych holds to 30 with an unreturnable serve.
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You either laugh or cry after an opening defeat like Tomas Berdych's thrashing by Stan Wawrinka. BBC 5 live sports extra commentator David Law says Berdych "likes a good laugh" and that after his first round defeat he simply tweeted a picture of a monkey with its eyes covered.
See no evil...
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*Berdych 1-0 Cilic
It's the worst possible start for Marin Cilic as he slips to 0-40 down in the blink of an eye. But the Croatian responds well, digging in and fighting back to deuce with a kick second serve. With the unforced error count well into double figures, Berdych injects some pace from the back of the court and breaks serve when Cilic dumps a forehand into the net.
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Tim Henman
former British number one on BBC Two
"There are a lot of similarities between them and I don't think either of them defend that well. It's about who can get on the front foot and who can restore some pride after dismal first round performances.
"If I'm going to pick a winner, I'm going to go for Cilic."
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Back to the here and now then. The warm-ups are complete and Marin Cilic is serving to Tomas Berdych. Let's play tennis.
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Murray's latest BBC Sport column has just gone live on the website. In it, he weighs up the challenge of facing Federer and even name-drops Liam from One Direction. Have a gander.
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If these players were looking for inspiration from anywhere, they should look no further than Andy Murray. The British number one recovered from a 6-4 6-4 defeat at the hands of Kei Nishikori to beat Milos Raonic 6-3 7-5 on Tuesday and set up a Group B showdown with Roger Federer on Thursday night.
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Piers Newbery
BBC Sport at the O2 Arena in London
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Tomas Berdych was thumped 6-1 6-1 by Stan Wawrinka in his first matchImage caption: Tomas Berdych was thumped 6-1 6-1 by Stan Wawrinka in his first match
"This afternoon's match might not be the most anticipated of the week but it made little difference to the huge queues snaking through the gates at the O2, and after six straight-sets wins there is no reason why this must-win clash shouldn't be the match of the tournament so far.
"Let's face it, Berdych and Cilic should be fairly fresh after spending a combined one hour and 54 minutes failing to trouble Wawrinka and Djokovic on Monday. And it could be worse, poor old Gaston Gaudio got a 6-0 6-0 thumping by Federer in Shanghai nine years ago."
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Tomas Berdych is ranked higher than Marin Cilic and has the edge in their head-to-head record. Cilic, however, has won more career titles, including this year's US Open.
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It's the tennis equivalent of a relegation six-pointer. A basement battle between the two whipping boys of the ATP World Tour finals so far. *Other football-related cliches are available.
In their first Group A matches, Marin Cilic and Tomas Berdych won precisely four games between them. The Croat and the the Czech are currently charging their glasses in the last chance saloon and you can follow their every sip and swig right here with us. *Other drinking-related cliches are available.
Live Reporting
Sam Sheringham
All times stated are UK
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Getty ImagesCopyright: Getty Images Tomas Berdych was thumped 6-1 6-1 by Stan Wawrinka in his first matchImage caption: Tomas Berdych was thumped 6-1 6-1 by Stan Wawrinka in his first match 
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Latest PostPost update
So, we're two and half days in and I think it's fair to say that this tournament hasn't really come to life. Let's hope Novak Djokovic and Stan Wawrinka can change all that tonight. Join us at 1945 for live text and radio coverage of the world number one against the Aussie Open champion. Catch you then.
Post update
Tim Henman
Former British number one on BBC Two
"That's two very disappointing matches for Cilic. He is 6 ft 6 ins with a big serve and he has lost four sets and only won six games. He's just not doing the basics right and he won't be a happy man."
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The match stats don't make pretty reading for Cilic. He only won 61% of points on his first serve and 41% on second, compares with his opponent's 71% and 70%. His serve was broken four times in two sets and he only won 43 out of 106 points.
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Nice line Tomas. That match lasted 74 minutes. Berdych is now 0-5 in opening matches in the World Tour Finals and 5-0 in second matches.
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Tomas Berdych: "I was really trying to focus on my tennis and my game, trying to go point by point. I think today was more fighting and getting through. It's good to have a win and it always counts.
"It's not my first year. I have the experience of losing the first match in the past and I know how to come back. I think that was the biggest difference today.
Asked about facing Djokovic next, Berdych asks the crowd "Any tips? I will need some. I just want to try to bring my best tennis and we'll see what happens. I hope I can have a great match."
Game, set and match Berdych
Berdych 6-3 6-1 Cilic
Talk of an early bath here, but have we spoken too soon? Berdych pushes a forehand into the tramlines to give Cilic a break point but snuffs it out with ace number five. Another one is saves, but two points later we're at match point. And the contest ends, somewhat fittingly, with a Cilic backhand into the net.
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*Berdych 6-3 5-1 Cilic
Cilic is officially his own worst enemy. A dreadful drop shot and a powerpuff approach earns Berdych three virtual match points. Cilic saves one with possibly his best shot of the match, but cannot sustain that level and nets to leave Berdych on the brink.
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Berdych 6-3 4-1 Cilic*
From 30-30, Cilic fails to get a ball back into play and Berdych is closing in on the match now. Goran Ivanesevic has had enough. He looks like a father whose son has just been sent off for diving in an under-11s match.
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David Law
BBC Radio 5 live sports extra commentator
"This is wild tennis at the moment for Marin Cilic - he is all over the place at the moment. This must be a nightmare if you are a professional athlete, surrounded by this sort of crowd, and it is just not working - you must want the ground to swallow you up.
"You can see the irritation and strain in his features after every point. Yet there's a calmness and serenity about Berdych."
Get involved via #bbctennis
Andrew Mark Spence: "Despite this performance in this match, I see Cilic winning a second Slam in '15...possibly Wimbledon."
Sam Hedge: "London should permanently host this event. The O2 arena has a unique atmosphere."
James Donald: "Both of these players are trying to hit themselves into form. Expecting to see a lot of unforced errors but also some huge shots."
Post update
*Berdych 6-3 3-1 Cilic
Cilic certainly has plenty of fans in the O2, judging by the number of Croatia football shirts in the crowd. But can he give them something to cheer about? Berdych plays a superb point to level up at 30-30, then lands a backhand right on the line to gain a break point. Another horrible rushed backhand from Cilic gives Berdych the game.
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Berdych 6-3 2-1 Cilic*
Thank goodness Tim Henman and Andrew Castle have healthy heads of hair because they are tearing it out in exasperation over Cilic's performance here. He opens up two break points but slops a second serve return into the net. Berdych gets back to deuce, and puts the game away thanks to another backhand howler from Cilic.
Get involved
John McEnerney: This may go the distance once MC finds his rhythm both big hitters plus Goran is there in MC's corner! Please 3 sets lads!
Andrew Mark Spence: "Despite this performance in this match, I see Cilic winning a second Slam in '15...possibly Wimbledon."
Sam Hedge: "London should permanently host this event. The O2 arena has a unique atmosphere."
James Donald: "Both of these players are trying to hit themselves into form. Expecting to see a lot of unforced errors but also some huge shots."
Post update
*Berdych 6-3 1-1 Cilic
Cilic just can't find any consistency out there. from 40-0 he lets Berdych back in the game with a couple of unforced errors, but stumbles over the line when the Czech nets a backhand. Coach Goran nods approvingly.
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Tim Henman
former British number one on BBC Two
"Berdych did a good job in the first set. He kept his first serve percentage high and moved forward when he got the chance. He'll be looking for more of the same. Whereas Cilic has to cut those unforced errors out and look to get on the offensive in these points when he's facing the serve."
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Berdych 6-3 1-0 Cilic*
Berdych is riding the wave now, hitting the spot with his serves and keeping his opponent guessing. He holds to 15 with a fizzer tot he corner that wrong-foots the big Croat.
Rise of the super coaches
The debate around who Tomas Berdych will bring in to his coaching set-up intensified after his first round battering.
The Czech said he wants to add somebody with a "new and different experience" - his current coach Tomas Krupa, who spent two months inside the top 300 in late 1995, helped Berdych to the Wimbledon Final in 2010.
BBC commentator Andrew Castle wonders if that would be "hard to take" for Krupa, while former British number one Tim Henman says: "It is an interesting concept that has really come into the game in the last few years - talk of these 'super coaches'.
"We thought it might be [eight times Grand Slam singles title winner] Ivan Lendl, but he said no. It will be intriguing to see who it is."
Game and first set Berdych
*Berdych 6-3 Cilic
Berdych doesn't waste any time in snaffling his opportunity. Two set points: the first is missed, the second taken when a Cilic forehand misses the line by a hair's breadth. 1-0 to the Czech.
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Berdych 5-3 Cilic*
Hold on, is this the Cilic charge? A heavily top-spun approach and a brutal overhead give him an opening at 0-30 on the Berdych serve. Then another dart to the net and a backhand volley sets up two break points. Berdych saves the first with a brilliant backhand winner and the second when Cilic lets himself down with a loopy drive past the baseline. There's no second chance for Cilic as Berdych moves to within one game of the set.
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Tim Henman
former British number one on BBC Two
"There's been 44 points but only six winners - that's 38 points ending in either an error or a forced error. I'm not suggesting they keep the ball in the middle of court and don't miss, but when there's that many mistakes you've got to be aware of it. They've got to get rid of them."
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*Berdych 4-3 Cilic
Cilic is having to work like a dog just to win a point. He slips to 15-40 down, but fights back to win the game with some booming serves and a drilled crosscourt backhand.
Bowl half full
Piers Newbery
BBC Sport at the O2 Arena in London
"This match looked like being the hardest sell of the week and not surprisingly, the upper bowl is probably only half full. Spaces in the lower bowl are far fewer, however, and it's a mark of the success of this event that a relatively low-key contest like this can attract well over 10,000 spectators paying top whack on a weekday afternoon."
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Berdych 4-2 Cilic*
The rallies are getting longer. The quality higher. But still Berdych is looking the likelier to run away with the spoils. He holds to love when Cilic goes long. Too long.
His coach Goran Ivanesevic looks a bit anxious in the crowd. Goran reached the semi-finals of this tournament three times.
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*Berdych 3-2 Cilic
Cilic so far looks a shadow of the player who stunned everyone to win his maiden Grand Slam title at Flushing Meadows. For every big serve and crunching groundstroke there's an elementary mistake. Luckily the pros outweigh the cons in this game and the Croat stays in touch.
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Dominic Inglot
British doubles player on BBC Radio 5 live sports extra
"Marin Cilic said in his interview after this last match that he was shanking a lot of shots, and there's already been a few out there today. It's nice to see that even some of these big names still make rookie mistakes."
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Berdych 3-1 Cilic*
Both players are gaining plenty from their second serves and Cilic can't contend with a couple of big kickers from Berdych. The Czech puts the game to bed with an easy smash.
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*Berdych 2-1 Cilic
Good signs from the 6ft 6ins Cilic. There's much more power and purpose about his serve and ground-strokes here as he comfortably holds to love.
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Berdych 2-0 Cilic*
Berdych, 29, reached the semi-finals of the ATP Tour finals in 2011. Cilic is making his debut at the tournament. And it's turning out to be a pretty miserable debut so far as Berdych holds to 30 with an unreturnable serve.
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You either laugh or cry after an opening defeat like Tomas Berdych's thrashing by Stan Wawrinka. BBC 5 live sports extra commentator David Law says Berdych "likes a good laugh" and that after his first round defeat he simply tweeted a picture of a monkey with its eyes covered.
See no evil...
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*Berdych 1-0 Cilic
It's the worst possible start for Marin Cilic as he slips to 0-40 down in the blink of an eye. But the Croatian responds well, digging in and fighting back to deuce with a kick second serve. With the unforced error count well into double figures, Berdych injects some pace from the back of the court and breaks serve when Cilic dumps a forehand into the net.
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Tim Henman
former British number one on BBC Two
"There are a lot of similarities between them and I don't think either of them defend that well. It's about who can get on the front foot and who can restore some pride after dismal first round performances.
"If I'm going to pick a winner, I'm going to go for Cilic."
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Back to the here and now then. The warm-ups are complete and Marin Cilic is serving to Tomas Berdych. Let's play tennis.
Post update
Murray's latest BBC Sport column has just gone live on the website. In it, he weighs up the challenge of facing Federer and even name-drops Liam from One Direction. Have a gander.
Post update
If these players were looking for inspiration from anywhere, they should look no further than Andy Murray. The British number one recovered from a 6-4 6-4 defeat at the hands of Kei Nishikori to beat Milos Raonic 6-3 7-5 on Tuesday and set up a Group B showdown with Roger Federer on Thursday night.
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Piers Newbery
BBC Sport at the O2 Arena in London
"This afternoon's match might not be the most anticipated of the week but it made little difference to the huge queues snaking through the gates at the O2, and after six straight-sets wins there is no reason why this must-win clash shouldn't be the match of the tournament so far.
"Let's face it, Berdych and Cilic should be fairly fresh after spending a combined one hour and 54 minutes failing to trouble Wawrinka and Djokovic on Monday. And it could be worse, poor old Gaston Gaudio got a 6-0 6-0 thumping by Federer in Shanghai nine years ago."
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Tomas Berdych is ranked higher than Marin Cilic and has the edge in their head-to-head record. Cilic, however, has won more career titles, including this year's US Open.
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It's the tennis equivalent of a relegation six-pointer. A basement battle between the two whipping boys of the ATP World Tour finals so far. *Other football-related cliches are available.
In their first Group A matches, Marin Cilic and Tomas Berdych won precisely four games between them. The Croat and the the Czech are currently charging their glasses in the last chance saloon and you can follow their every sip and swig right here with us. *Other drinking-related cliches are available.