UMMC Ekaterinburg took a big step towards Group C supremacy by beating Spanish powerhouse Ros Casares 89-81 on Wednesday in front a 6,500-crowd in Russia.
Laurent Buffard's Russian giants improved to 3-0 while Ros dropped to 1-2.
The Valencia outfit led 43-28 at half-time but were pegged back in the third quarter when Ekaterinburg outscored them 24-9 to leave the game knotted at 52-52.
Ekaterinburg looked to be headed for victory at the end of regulation but Amaya Valdemoro's basket with 1.5 seconds remaining tied the game at 76-76 to force overtime.
The home side then marched to victory.
USA international Cappie Pondexter hit a couple of baskets at the start of the extra period for Ekaterinburg as they opened up a commanding 85-78 lead.
Isma Canto, the Ros Casares coach, wasn't too downhearted.
"We had the opportunity to win on a very difficult court but we are left with a bitter taste," he said.
"However, we have shown that we are able to compete against the best Russian teams."
Pondexter, who joined Ekaterinburg shortly before the season from Fenerbahce, had a game-high 23 points but finished with just three assists and six turnovers.
Polish international Agnieszka Bibrzycka poured in 22 points and like Pondexter pulled down five rebounds but also came up with a team-high four steals.
Spain national team ace Valdemoro had 22 points to lead Ros Casares in scoring while Brazilian Erika De Souza scored 16 and added game highs in rebounds (15) and steals (five).
Team USA's Delisha Milton-Jones also poured in 15 points and grabbed eight rebounds for Ros and Elisa Aguilar scored eight points and dished out seven assists.
Ros out-rebounded Ekaterinburg 40-30 while the Russians shot the ball better from long range, hitting seven of 15 (46.7%) to just five of 18 (27.8%) for the Spanish team.