Radhi Jaidi has picked up a thigh injury.
Blues will go into Saturday's game at Burnley without the services of defender Radhi Jaidi who has picked up an injury whilst on international duty with Tunisia.
Jaidi sustained a thigh strain in training with his country and was forced to pull out of their squad for the matches against the Seychelles and France.
Boss Alex McLeish admitted that the 33-year-old would be missed having produced what he described as 'three stormers' since being recalled in preference to Martin Taylor.
But the Blues boss gave his full backing to Taylor, who did little wrong during his stint in the side early in the season.
"Jaidi picked up an injury in training with Tunisia and didn't even get to play in their games," explained McLeish.
"Whether he has been unlucky or whether it was a heavy training session he didn't really need, I don't know.
"I can't really second-guess what the Tunisians were doing in training. I would like to think that it wasn't excessive training that's done this to him.
"Radhi has been excellent. He's come back in and had three stormers.
Martin Taylor will return to the centre of defence for Saturday's trip to Burnley.
"But Tiny (Taylor) will come back in for him. He started the season very solidly and he's got to give us those kinds of performances again."
McLeish said that he expected Jaidi to be sidelined for three games (Burnley, Crystal Palace and Sheff Wednesday).
Blues will also be without Stephen Kelly (thigh) and Damien Johnson (back).
McLeish added: "You think you've got a big squad and you're looking at the subs' bench and leaving top players off the bench, like I've had to do with McSheffrey and Bent recently.
"Then you get one or two injuries and suddenly you're down to 15 or 16 players. On Saturday we've only got cover of one defender, Franck Queudrue."