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By Chris Bevan
Federer 0-1 Del Potro
Not the greatest start by Fed, with Del Potro gifted an early break at 30-all when his limp backhand clips the net and dies at Federer’s feet. A mis-hit by the Argentine brings us to deuce but his blistering forehand soon sets up another break point only for him to waste it with a wild shot from the same flank. Chance gone No. Fed runs round a forehand but puts it in the tramlinees and, on the next point, goes long with a backhand. Del Potro has an early break, and I’m just getting my breath back.
** Denotes NEXT server
2057: Right then, we’re off. Federer to serve first2050: Fed and Del Potro are busy knocking up - so time to remind you lot how to get in touch tonight.Tweet me gently on Twitter,](http://twitter.com/chrisbevan_bbc)text me on 81111 or have your say on606.](http://www.bbc.co.uk/dna/606/A60052790)No more maths questions though, for a little while at least (my head still hurts from earlier).BBC Sport’s Piers Newbery Tweeting from the O2 Arena:](http://twitter.com/piersnewbery)"So everyone clear Federer & Del Potro are about to play a tennis match, the winner gets to play another one. I think. Lively crowd tonight."2047: Del Potro is first on court, giving the crowd a wave as he makes his way to his chair. He’s quickly followed by Federer too, following a quick pre-match interview in which the world number one says (with a smile) that he wants “revenge” for his defeat by Del Potro in the US Open final in September. Can’t be too often that Fed needs to get revenge, can it
From ArmchairPro on 606:](http://www.bbc.co.uk/dna/606/A60052790)"Re 2038. Wash your mouth out please Chris. We don’t need an epic contest we need a thrashing (either way works fine)!"BBC Sport’s 5livetennis Tweeting from the O2 Arena:](http://twitter.com/5livetennis)“ATP officials changed their minds about qualification scenarios three times in an hour! Shocking that organisers don’t know what’s going on…they’ve finally settled on the scenario they originally announced.”**2038: **Anyway, enough about the maths (for now, and hopefully for the rest of the night!). Let’s look forward to what is a mouth-watering showdown between Federer, the world number one, and Del Potro, who is ranked fifth. The Argentine has only won one of their seven encounters but what a win that was - a five-set epic in the final of this year’s US Open that gave the 21-year-old his first Grand Slam title. More of the same tonight please… oh, and the players are due on court at around 2045 GMT.
2036: Andy Murray on playing Fernando Verdasco knowing that a three-set win might not be enough to put him into the semi-finals: “It was tough, but I needed to win the match. I knew if I won the match then there was only one way I couldn’t go through, and that was Del Potro winning in three sets and then I think it would go down to the games won. I just had to focus on winning and then there’s a very slim chance of me going out.”
From Simon in Edinburgh via text on 81111: “So only a three set win for Del Potro can send Muzza out Surely sod’s law means that is inevitable and much calculator bashing will ensue.”
BBC Sport’s Piers Newbery Tweeting from the O2 Arena:](http://twitter.com/piersnewbery)“Murray on the qualification system - ‘I don’t know why everyone makes it sound so complicated. The people that go through deserve to’.”
2028: Don’t understand who will go through should Del Potro beat Federer in three sets Let me explain (or, more accurately, let me allow my colleague Matt Braithwaite explain). Here’s the current win-loss standings between the three men in contention, and their win percentage: Federer W32 L22 (59.259%) Murray W44 L43 (50.575%) Del Potro W27 L31 (46.550%)
What does that mean A three sets win by Del Potro, with a winning margin by fewer than five games means Fed and Murray are through. A three sets win by JMDP with a margin of five to nine games puts Del Potro and Fed through (UNLESS two sets go to tie-breaks, in which case JMDP has to win the other set 6-0 for that to apply). And, if Del Potro wins in three sets by a margin of 10 games or more, then he and Murray go through.
2026: Here’s the lowdown then (deep breath): Any win for Federer means he and Murray are through. A straight sets win for Del Potro means he and Murray are through. A three-set win for Del Potro means we go down to percentage of games won. (More on that in a minute).
From Caludrup on 606:](http://www.bbc.co.uk/dna/606/A60052790)“It must be very strange for a tennis player to rely on other results. Probably every other match of their careers is a cut and dry, win or lose scenario. This is tension like no other tournament in tennis can create - three of the top five battling each other and mathematics, I can’t wait!”
2024: In case you missed all the excitement earlier, Andy Murray’s three-set win over Fernando Verdasco means the British number one will have to wait until the end of tonight’s match to find out whether he has reached the semi-finals of the ATP World Tour Finals. It’s fair to say there was a bit of confusion over what result will send Murray through from Group A but, luckily, that appears to have been cleared up. My head still hurts though.
2020 GMT: Evening all. After the way things have gone so far today, don’t be surprised if Roger Federer and Juan Martin del Potro come out on court at the O2 Arena wielding calculators rather than tennis racquets - like you and I, they could well end up needing them..This article is from the BBC News website. © British Broadcasting Corporation, The BBC is not responsible for the content of external internet sites.