Birmingham will run the rule over Hayden Mullins and Rob Hall ahead of Friday night's televised visit of Middlesbrough.
Midfielder Mullins was forced off late on in Tuesday night's 1-1 draw at Blackpool nursing a groin injury although it is not as bad as first feared.
On-loan winger Hall missed out altogether having been struck down with a sickness bug in the build-up to the game and remains doubtful.
Manager Lee Clark will assess both closely, with Hall boasting a real chance of starting against Boro should he prove his availability while Mullins' place has come under threat from Papa Bouba Diop following his solid cameo at Bloomfield Road.
Clark must also decide whether or not to reinstate captain Steven Caldwell having dropped the centre-back to the bench in midweek, while it will be hoped right-back Paul Caddis can handle two games in four days after 10 weeks out with a dislocated shoulder.
Full-backs David Murphy and Stephen Carr (both knee) are long-term absentees while striker Akwasi Asante (hamstring) remains sidelined for the immediate future.
Middlesbrough midfielder Grant Leadbitter is facing a battle to be fit.
The 26-year-old midfielder missed the 3-0 victory over Huddersfield in midweek through suspension after reaching five bookings for the campaign.
However, he would have been sidelined anyway by a calf problem, and he is now fighting against the clock to be ready for the game at St Andrew's.
Manager Tony Mowbray will otherwise have a trio of key players missing with full-back George Friend (hamstring) and central defender Jonathan Woodgate and midfielder Faris Haroun (both calf) having all been ruled out for a fortnight earlier this week.
Defender Rhys Williams (ankle ligaments), midfielders Julio Arca (toe) and Muzzy Carayol (knee) and striker Curtis Main (also knee) are all working their way back towards full fitness, but are still out of contention.