James Blake fought back from a set and a break down to all but book his place in the Masters Cup semi-finals with a 2-6, 6-4, 7-5 victory over Russian Nikolay Davydenko on Wednesday.
The American rediscovered the mental resilience that got him past Rafael Nadal on Monday and will reach the last four if the world number two beats fellow Spaniard Tommy Robredo in the later Gold Group match.
World number three Davydenko, who looked to be cruising to victory in the second set, will need to overcome Nadal in his final round robin match to have a chance of reaching the knockout stage for the second successive year.
Blake, whose big match temperament has been questioned in the past, lost his first five service games but bounced back to claim his fifth victory in five attempts against the hard-working Davydenko.
Both players struggled with their serves early on and the first five games of the opener were breaks with Davydenko the first to break the cycle by holding for a 4-2 lead before racing through the next two games to take a one set lead.
World number eight Blake thought he had finally held serve in the first game of the second set but Davydenko's Hawkeye video appeals reversed an ace and a lob on the same game point and the Russian broke again.
Davydenko, who played some sublime tennis to win the Paris Masters two weeks ago, continued to have the upper hand before Blake suddenly found his range to break back for 4-4 and levelled the match with another break two games later.
The 24-year-old New Yorker converted his second break point to go up in the deciding set but Davydenko broke back immediately and a tiebreak looked inevitable.
By now, though, Blake was pouncing on anything loose the Russian sent down at him and, leading 6-5, the American grabbed advantage by lashing a beautiful return into the corner and won the match when Davydenko went wide on the next point.