Birmingham forward James McFadden will be out of action "for the foreseeable future" after suffering anterior cruciate ligament damage in training on Friday.
The 27-year-old Scotland international will see a specialist on Monday with a view to undergoing surgery on the injury.
A club statement on Friday evening read: "Birmingham City can confirm that James McFadden sustained anterior cruciate ligament damage to his left knee in training today.
"McFadden will see a specialist on Monday with a view to surgery and will be out of action for the foreseeable future."
McFadden has featured in all four of Blues' Barclays Premier League games so far this season as well as Scotland's opening two Euro 2012 qualifiers earlier this month.
The former Motherwell and Everton striker's only goal of the campaign to date came in last month's Carling Cup victory over Rochdale.