Former Rovers player Bentley is suffering from a groin problem while Jiranek has not recovered from the toe injury which required surgery.
Eight-goal leading scorer Nikola Zigic and fellow striker Obafemi Martins are given only a 50-50 chance of being fit by Blues boss Alex McLeish.
The duo are both troubled by groin injuries while, in addition, Zigic also has concerns over a hip problem.
James McFadden and Scott Dann remain on the sidelines with knee and hamstring problems and are unlikely to return from long-term lay-offs this season.
Source: PA
Source: PA