Aston Villa defender Martin Laursen will be out of action for up to three months with medial ligament damage.
A scan has confirmed Laursen's worst fears after he sustained the injury during Wednesday's Carling Cup defeat against Chelsea at Stamford Bridge.
The 29-year-old Danish international left the ground on crutches and is now facing the prospect of being sidelined until the New Year.
It is the latest blow for Laursen who has been dogged by knee problems since his £3million move from AC Milan to Villa Park in the summer of 2004.
Laursen played only a handful of games in his first two seasons with Villa but surgery in the United States appeared to have helped the problem, and he has impressed when given a first-team chance this season.
Villa manager Martin O'Neill said: 'Martin has got medial ligament damage and it is not looking so good for him. He is going to be out for quite some time, possibly up to three months.
'The only consolation is it's the other knee and not the one where he has experienced his other problems. But you have to feel great sympathy for him because he has worked so hard to get back to fitness.
'The way he has improved from the way he was during pre-season has been terrific and he did well when he came into the team against the likes of West Ham, Watford and Blackburn.'
Skipper Gareth Barry is also likely to miss tomorrow's game at Everton after suffering severe bruising to his back against Chelsea.
Barry attempted to train today but was in considerable discomfort and is unlikely to be ready for the game at Goodison Park.