Birmingham boss Steve Bruce has admitted he made two bids for current Premiership players as he looks to bolster his injury-hit defence.
Bruce has all five of his recognised centre-halves out of action and is being linked with Leeds' Michael Duberry and Arsenal's Matthew Upson.
The Blues chief has already brought in Bordeaux striker Christophe Dugarry and Lens full-back Ferdinand Coly on loan until the end of the campaign.
But it is the middle of the defence that is giving him the most cause for concern with Darren Purse, Kenny Cunningham, Michael Johnson, Steve Vickers and Olivier Tebily sidelined.
He had to partner right-back Jeff Kenna and rookie Joey Hutchinson in Sunday's 3-1 FA Cup reversal by Fulham at Loftus Road.
"Cunningham will be out for six weeks, Purse for another four weeks and Tebily for three months. We can't afford to have five centre-halves missing. It is a cause for concern," Bruce said.