Rubin Kazan coach Kurban Berdyev said his side cannot rely on Barcelona resting a host of star players when the two clubs meet on Tuesday.
Barcelona have already qualified for the knockout stages and are free to tinker with their line-up, while Rubin are one point behind second-placed FC Copenhagen and a mathematical chance of progressing.
To do so, Rubin will need to secure the three points at the Camp Nou and hope that Greek champions Panathinaikos can hold or upset Copenhagen in Denmark.
While the notion of Rubin defeating Barca seems improbable, it happened as recently as last season, when the Russian club stunned the Catalan giants 2-1 in Barcelona.
Barca have rested Xavi, Daniel Alves, Pedro Rodríguez and David Villa for Tuesday's match, but Berdyev acknowledges that Pep Guardiola's men will still pose a difficult challenge.