Anthony Randolph and Chris Singleton led Lokomotiv Kuban into their first Euroleague play-offs with 17 points apiece in their 86-62 win over Crvena Zvezda.
Lokomotiv knew victory on Thursday would secure their place in the last eight and, after a sluggish start, they quickly found their rhythm, Randolph scoring nine points in the first quarter to give them a narrow lead.
Three-pointers were the order of the day in the second as Lokomotiv stretched their advantage, with Singleton coming to the fore in the final quarter to complete the victory.
Panathinaikos' hopes of joining them in the top four in Group E looked to be over as Darussafaka Dogus led in the closing minutes, however the Greek side finished strongly to put them on the verge of progressing.
Their place depends on Anadolu Efes' clash with Unicaja on Friday, the former needing to win to stop Panathinaikos qualifying.
After trailing at the halfway stage, Panathinaikos surged into the lead in the third quarter, but needed Elliot Williams to secure the 86-84 win with two last-gasp free throws.
There was still time for Scottie Wilbekin to miss a three-pointer for Darussafaka, but Panathinaikos clung on to record a seventh win in their last eight matches.
In Group F's only match of the night, top-of-the-table CSKA Moscow suffered a surprise 91-83 defeat in Germany against Brose Baskets Bamberg.
Defeat for CSKA - who have already qualified for the next stage - has no effect on their place at the top of the group, but Bamberg's hopes of staying in the competition are still alive after a third win in a row.