Nikolay Davydenko survived a last-minute attack of nerves on Wednesday to beat Argentina's Gaston Gaudio for the first time and move within sight of the Masters Cup semi-finals.
The Russian spurned three match points before finally downing the world number nine 6-3, 6-4, ending a run of five straight defeats.
He had earlier beaten Andre Agassi in straight sets before the US veteran became the fifth big name to pull out of the 4.45-million-dollar season finale, citing an ankle injury.
Davydenko, 24, saved three break points in his first game before recovering to break Gaudio twice in the first set.
The Argentine, screaming and smashing his racquet to the floor, managed one break back and took Davydenko to six deuces at 5-2 before the Russian converted the first of two set points with an ace.
Further histrionics early in the second net could not stop Russia's top player breaking for 1-0 and Gaudio was then taken to deuce before holding for 2-1.
At 3-1 up, Davydenko was gifted another break of serve as Gaudio hit the net and went long twice.
But serving for the match, the world number seven wobbled and Gaudio converted the last of three break points for 5-3.
Davydenko spurned two match points on Gaudio's serve as he managed six deuces of his own against the 26-year-old Argentine.
GOLD GROUP: Nikolay Davydenko (RUS x5) bt Gaston Gaudio (ARG x7) 6-3, 6-4.
DOUBLES: Wayne Black/Kevin Ullyett (x3) bt Stephen Huss/Wesley Moodie (x8) 3-6, 7-6 (7/1), 6-2; Michael Llodra/Fabrice Santoro (x6) bt Jonas Bjorkman/Max Mirnyi (x2) 7-6 (7/3), 6-4.