Birmingham skipper Stephen Carr has been ruled out for up to six months after undergoing surgery on his knee.
The 36-year-old had been on the verge of a first-team comeback after shaking off a thigh problem, but he has now been ruled out until March at the earliest.
"Monday and Tuesday he was training really well prior to the Peterborough United game and we had pencilled him in to play, and he was really positive," manager Lee Clark told the Birmingham Mail.
"Prior to the game he felt a little problem in the knee so we ruled him out. Over the course of the next few days it became really swollen.
"We got him down to London for an appointment with the specialist, who worked with him last season, who went inside the knee and found quite a bit of damage.
"It's horrific news. It's huge blow for the club, but more importantly for the lad himself.
"He's going to be out for a minimum of six months."