James Vaughan is set to undergo surgery and will be sidelined for the rest of 2008.
The Everton forward suffered a knee injury in training on Friday and has now been assessed again by the club's medical staff.
It has been decided that the best solution is an operation, meaning Vaughan will be out of action for at least five weeks.
"James Vaughan twisted his right knee last Friday," Everton head physio Mick Rathbone told the club's official website.
"He will be out until the New Year. The only saving grace is that it is not the knee he has had so much trouble with in the past.
"It's a terrible shame for James after all the problems he's had in the past. But, unfortunately, that's football."
Vaughan has been plagued by injuries since his emergence in April 2005.