Leaders Spartak Moscow Region lost their 100% record after slipping to a 78-65 defeat against Wisla Can Pack at Vidnoje Basketball Centre.
The victory moves Wisla up to third place in Group A with a 3-4 record, while Spartak stay top on 6-1.
The hosts raced away to a 10-5 advantage midway through the first quarter, but Wisla fought back and a three-pointer from Jelena Skerovic handed the Polish side a 21-17 advantage at the end of the period.
The visitors extended their advantage with a 22-19 second-quarter performance, ensuring a seven-point interval lead.
Diana Taurasi's two-point effort pegged the deficit back to three points for Spartak midway through the third, but that was as good as it got for the Russians, who succumbed to busy Wisla in the latter stages.
A three-pointer from Monika Krawiec capped an 11-3 surge that saw the Poles restore their comfort zone as the game entered its final period.
Skerovic's successful free throw gave Wisla a game-high 14-point lead with 5:36 remaining as the Russians struggled to find an answer against a side they so convincingly beat on the road just last month.
Anna De Forge led the visitors with 21 points and three of four (75%) from three-point range, while the American guard also picked up nine rebounds on the defensive glass and added three assists.
Team-mate Daliborka Vilipic added 18 and picked up 11 rebounds.
Diana Taurasi top-scored with 11 for a disappointing Spartak side, who will be rueing gifting their opponents 23 free throws, from which Wisla added 15 points for a completion rate of 65.2%.