ATP World Tour Finals
Venue: O2 Arena, London Date: 22-29 November
Tournament coverage: Live on BBC Two, 28/29 November, 1430 GMT; every match live on BBC Radio 5 live/5 live sports extra; live text commentaries on BBC Sport website; live coverage every day on Sky Sports
Del Potro was made to work hard for victory against Verdasco
By Caroline Cheese
BBC Sport at the O2 Arena
Juan Martin del Potro kept his semi-final hopes alive with a tense win over Fernando Verdasco at the ATP World Tour Finals.
The US Open champion, who lost his opening Group A encounter against Andy Murray, came through 6-4 3-6 7-6 (7-1) to leave the Spaniard winless after two matches.
The result means Murray can reach the semi-finals with a victory over Roger Federer in Tuesday's evening match.
Del Potro, meanwhile, meets Federer in his final match on Thursday in a repeat of the US Open final, which the Argentine won in five sets.
"It's a different surface, so I will have to play better than the US Open if I want to win but it's a good chance to advance to the semis," said the 21-year-old.
Verdasco, who faces Murray on Thursday, must hope Federer beats the Scot to keep alive his slim chances of progress.
"I had an unbelievable opportunity today, and right now the chances for me to qualify are pretty low," said a downbeat Verdasco.
"It was pretty hard to lose the match after recovering the first set, but I tried my best and I was really close."
The first two days at the O2 Arena had provided drama, intrigue and upsets, but day three's opening encounter - between two of the biggest forehands in the men's game - only really took off at the end of the third set.
Verdasco started edgily in front of an expectant crowd of more than 15,000, and trailing 2-1 in the first set, the Spaniard mis-hit the simplest of forehands - usually his bread and butter.
That gifted his opponent two break points, and Verdasco erred on another forehand to put Del Potro a break up.
Del Potro's serve only came under threat at 5-4 but he saved two break points with big aces and wrapped up the first set in 38 minutes, pumping his fist in a rare show of emotion.
But Del Potro, who has been below his best since winning his maiden Grand Slam title at the US Open in September, toiled in the second set and a wayward game at 4-3 handed Verdasco the chance to serve for the second set.
The Argentine put up little resistance as Verdasco took the set, and Del Potro's sluggishness continued into the decider.
However, he came alive at 4-3 when he earned three break points. Having wasted two, he bravely stopped a rally to make a HawkEye challenge and threw his arms in the air in relief when he was proved correct.
The shackles were off and Del Potro, playing the sort of tennis which dazzled the New York crowds in September, raced to match point at 5-2.
Verdasco was not finished though, saving it with a huge forehand, and the crowd, itching to get involved, responded.
Del Potro retreated into his shell, an awful game allowing Verdasco to break back in the ninth game.
"Of course I was nervous, because I knew if I lost, I would probably be going home," Del Potro later admitted.
In an enthralling game at 5-4, Del Potro earned a second match point, but Verdasco, knowing his survival in the tournament was probably on the line, fought back again.
By now, it was impossible to pick a winner - and it seemed only appropriate the match should be decided by a tie-break.
But Verdasco's forehand crumbled under pressure and Del Potro closed it out 7-1 to seal victory after two hours and 23 minutes.
"The win was important for my confidence, and now I hope to play my best tennis against Roger," said Del Potro.
In the opening doubles match of the day, third seeds Mahesh Bhupathi and Mark Knowles closed in on a semi-final place with a narrow 3-6 6-3 10-7 win over Polish pair Mariusz Fyrstenberg and Marcin Matkowski.