Derby County defender Jake Rooney has suffered anterior cruciate ligament damage to his right knee.
Rooney underwent a scan on the injury on Monday, which he sustained in the opening stages of last weekend’s Sky Bet League One fixture at Bolton Wanderers, and the extent of the damage was confirmed.
Head Coach Paul Warne said: “It's heartbreaking news for Jake to suffer this injury.
“He had forced his way into the team in the last few games and done really well.
“It's tough being a young professional when you're trying to make your way in the game and to have this sort of injury is hugely disappointing. We are gutted for him, but he’s got our full support and we’ll do everything we can to help him get back in the best possible condition.”
Rooney, 20, has made 21 appearances for Derby since signing from Burnley last summer and recently signed a new three-year contract.