Birmingham midfielder Stephen Clemence has been ruled out for the rest of the season with a torn hamstring.
But Blues manager Steve Bruce is optimistic Nicky Butt could return to action for the derby with Aston Villa in nine days' time, as his hamstring injury is not as serious.
Clemence sustained his injury during Tuesday's victory over Bolton which moved the club out of the bottom three of the Premiership for the first time in six months.
The former Tottenham player went for a scan on the injury and his worst fears have been confirmed.
Bruce said: 'Clemence will not play again this season. He has torn his hamstring and you are looking at 28 days out of action with such an injury which basically takes you up to the end of the season.
'The good thing is we are more hopeful about Nicky Butt. His hamstring injury is not as severe. You are normally out for 10-14 days with a small strain and he possibly could be available for the Villa game.'
Butt, who also suffered his injury against Bolton, has started to produce his best form in recent weeks and his absence will be a blow.
But there was some good news for Bruce ahead of tomorrow evening's game at his former club Wigan.
Midfielders David Dunn and Muzzy Izzet, striker Chris Sutton and central defender Matthew Upson have all been declared fit and are in the squad to travel to the JJB Stadium.
Sutton, Izzet and Dunn have been back in training for 10 days although Upson only returned on Thursday after two months on the sidelines with groin and pelvic problems.