Lions, featuring a host of Great Britain stars, lost 70-67 at Castors Braine on Wednesday, despite a sterling effort from Jo Leedham-Warner.
It meant they needed results on Thursday to go their way. But Zabiny Brno beat Rutronik Stars Keltern 78-77 and Ensino lost to Valencia to hand Mark Clark’s team passage through via their third-place group finish.
The Lions now face face French side Bourges, with whom Leedham-Warner won the competition in 2016, in a two-legged battle.
GB’s Azania Stewart, Holly Winterburn, Shanice Beckford-Norton, Chantel Charles and veteran Leedham-Warner have excelled to keep Lions unbeaten in WBBL action so far this season as well as progressing to the knockout rounds in Europe.
The Play-Off round one contenders will match up in home-and-away two-leg ties, with the higher-ranked team playing the return leg at home. The first leg is scheduled for Wednesday, 15 December and the return fixtures will take place on Wednesday, 22 December.
The teams that emerge from Play-Off round one will continue in the Round of 16, which will follow the same home-and-away format.
The Round of 16 is set to tip off on January 13, 2022 with the return leg scheduled for January 20, 2022.