Tomas Berdych remains in the hunt for a place in the semi-finals of the ATP World Tour Finals after he battled back to beat Serbia's Janko Tipsarevic 2-6, 6-3, 7-6 (8/6) on Wednesday.
Berdych, who lost his opening game against Novak Djokovic, looked on the way out when Tipsarevic, playing in place of the injured Andy Murray, held a match point in the final set tie-break, but the Czech seventh seed recovered to seal a crucial Group A victory at London's O2 Arena.
Now Berdych has to beat David Ferrer in his last match on Friday and hope other results go his way to reach the semis, while Tipsarevic's participation is likely to end with his final fixture against Djokovic.
With nothing to lose and a place in the semi-finals still up for grabs, Tipsarevic was able to swing freely at the start and his ground-strokes caused Berdych problems as he broke in the opening game of the first set.
Tipsarevic, who has a quotation from Russian writer Dostoevsky tattooed on his left arm and plays in perspex glasses, has always been one of the Tour's more flamboyant and intriguing talents.
At the age of 27 he is finally delivering on his potential - appearing in the Tour Finals for the first time after surging up to ninth in the rankings on the back of a US Open quarter-final appearance and ATP titles in Kuala Lumpur and Moscow.
He broke again for a 4-1 lead before saving three break points on his own serve to seal the set.
But 2010 Wimbledon finalist Berdych had given world number one Djokovic a run for his money on Sunday, holding a match point before eventually losing a final set tie-break, and the Czech gradually built up a head of steam again.
The 26-year-old's big serves kept Tipsarevic at bay and allowed him to concentrate on breaking the Serb, which he eventually did with some bruising forehands in the eighth game to land the decisive break in the second set.
Berdych saved a break point early in the third set and matched Tipsarevic blow for blow from the baseline.
A tie-break was required to finally separate them and it was Berdych who came out on top in dramatic fashion.
Tipsarevic had a match point at 6-5 on his serve but he opted to rush to the net and could not control his volley, which landed agonisingly wide of the tramlines.
He then slipped on Berdych's first match point, leaving the whole court open for the Czech to hit an easy winner while Tipsarevic lay prone on the floor.