Birmingham will assess the seriousness of Curtis Davies' ankle injury over the coming days.
The centre-back went down in pain late on in Saturday's 1-0 home defeat to Huddersfield but after lengthy treatment, shunned an available stretcher to hobble down the touchline and back to the dressing room.
Manager Lee Clark suggested afterwards the injury was not as bad as it could have been, but a full assessment will be required before determining the extent of the problem.
"I've seen the footage and I'm a lucky manager really because Curtis could easily have dislocated/broken his ankle," Clark said. "It's awful. We're lucky.
"We might not be because he could be out - we don't know yet, it's too early to say. But it certainly could have been one where it was diagnosed like that (on the spot), for what he's done."
Birmingham are experiencing huge injury problems in defence this term with Stephen Carr (knee), Paul Caddis (shoulder), David Murphy (hamstring), Pablo Ibanez (broken toe) and Will Packwood (back) all missing at the weekend, while Davies followed James Hurst (cramp) off the field.