Conor McAleny has suffered a broken leg and is expected to be out for most of the 2013/14 season.
The young Blues striker, who is on loan at Brentford, suffered a fracture to his right tibia during the Bees' League One match against Walsall on Saturday.
McAleny suffered the injury when he challenged for the ball with Walsall's Adam Chambers.
Brentford manager Uwe Rosler was quick to absolve the Saddlers player from any blame.
"Conor was coming in from the side and he wanted to shoot," he said. “Things like this can happen in football. I don’t think the player went for him.”
Rosler also expressed his concern for McAleny after watching him stretchered from the field.
“I feel for the lad," he said. "He is a very promising player and a very good character. We will give him all the support we can and hopefully he will come back soon.”
Everton Under-21s manager Alan Stubbs said: "It's bitterly disappointing for Conor and I really feel for him. He was doing well down there, getting some game time and Brentford enjoyed having him. But things like this can happen and we'll be here to help him back to full fitness."
McAleny is currently being treated in the Brentford area but he will return to Finch Farm later this week to begin his long period of recovery and rehabilitation.