Birmingham City have revealed that James McFadden will be out of action "for the foreseeable future" after the Scotland international suffered anterior cruciate ligament damage during training on Friday.
The 27-year-old will see a specialist on Monday and may have to endure an operation on the problem.
A club statement read: "Birmingham City can confirm that James McFadden sustained anterior cruciate ligament damage to his left knee in training.
"McFadden will see a specialist on Monday with a view to surgery and will be out of action for the foreseeable future."
Meanwhile, Scotland manager Craig Levein said of the former Motherwell star: "I know more than anyone how devastating a cruciate ligament injury can be and my sympathies go to James.
"Having said that, he's a strong character and I'm sure he will overcome it.
"I'm not even going to get into what this means for Scotland because at this stage the most important thing is that he recovers and gets his career back on track.
"On behalf of the squad, the backroom staff and, I'm sure, the Scotland supporters, I wish him a speedy recovery."