Reading have confirmed midfielder Jem Karacan has suffered a ruptured anterior cruciate ligament.
He sustained the injury against Leeds a fortnight ago and will undergo an operation this week before beginning his lengthy rehabilitation.
He told the club website: "I know the rehab and what I need to do to get back to full fitness. It's going to be a long journey, but one I'm willing to throw myself at.
"The main thing is mentally getting your head around it. It's gutting, it's frustrating - every day of my life is football. I'm missing it already. But I've come back from an injury before.
"The medical staff are brilliant, they'll keep my spirits up and make sure I do all my rehab. Hopefully I can be back sooner than expected."