Andy Murray produced some of his most resourceful tennis to beat Russia's Dmitry Tursunov and reach the semi-finals of the St Petersburg Open.
Murray won 3-6 7-6 (7-2) 6-4 after brilliantly saving 12 of the 14 break-points against him in the match.
The second seed now plays another Russian, 2004 champion Mikhail Youzhny, for a place in Sunday's final.
The Briton still has a slim chance of qualifying for the Masters Cup but would realistically need to win here.
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Three places remain up for grabs for the end-of-season event in Shanghai, with David Ferrer likely to take one of them.
Youzhny is one of Murray's rivals for the remaining two places and next week's Masters Series tournament in Paris is the last chance to earn qualifying points.
Fifth seed Tursunov, cheered on by his home crowd, played the smarter tennis in the first set, twice breaking the Scot who had trouble with his serve and double-faulted twice.
But Murray, who had beaten the world number 27 in both their previous meetings, hit seven aces in the second set, which went to a tie-break.
"He had so many chances on my serve he probably deserved to win the first two sets"
The world number 16 from Dunblane suddenly found his top form, winning the breaker easily, only to see Tursunov manufacture three break-points in game six of the final set.
But the Scot held before immediately breaking the Russian with the second of just three break-points he created in the entire match.
Murray was then in position to serve out for the win, and closed out the match in a shade under two-and-a-quarter hours.
"He had so many chances on my serve he probably deserved to win the first two sets," said Murray.
"But I made a lot of great first serves and in the tie-break I won every point on my serve.
"I also changed my tactics towards the end of the second set, started to play more aggressive and come to the net a bit more."
Murray said his match against Youzhny, 25, who is seeded third and is ranked 19th in the world, would be "a different match against a different type of player".
Youzhny's quarter-final opponent, Philipp Kohlschreiber, retired after losing the first set when he felt unwell.
The other semi-final will see Fernando Verdasco of Spain, the number six seed, take on Marin Cilic after the Croat qualifier overcame Latvia's Ernests Gulbis 6-4 6-4.
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