The Russians trailed 20-14 after the opening quarter but hit back to win their 16th straight.
Scoonie Penn missed a pair of free throws for the Greeks in the final six seconds to leave them needing to beat DKV Joventut next week to reach the last eight.
Partizan Belgrade kept their Euroleague hopes alive, overcoming a nine point half-time deficit to down DKV Joventut in Badalona.
Uros Tripkovic scored 26 as the Serbs bounced back from 50-43 behind at the half to win 89-80.
Barcelona's hopes of home-court advantage in the quarter-finals all but disappeared as they lost in Turkey as Efes Istanbul recorded their first Top 16 win, 82-78 on the back of a 25 point performance from Marcus Haislip.
The hosts were already eliminated after losing their first four games but Kerem Gonlum scored ten points on the bounce that allowed Efes to take a 46-39 lead at half-time.
Gonlum finished with 18 while Haislip also had 11 rebounds. Juan Carlos Navarro had 16 points for the Catalans who were already assured of a quarter-final berth.
Treviso ensured that Group G will go down to the wire as they coasted past winless Aris Thessaloniki 83-72.
The Italians charged into an 11 point lead after ten minutes and held on with Preston Shumpert top-scoring with 17 as five players notched double digits.
Benetton plus Unicaja Málaga and Dynamo Moscow. who meet on Thursday, are tied in a three-way log jam at the top of the pool with six points.