Aston Villa striker Chris Sutton will be out of action until mid-February because of blurred vision and concussion.
The former Celtic player suffered the setback during the early stages of last weekend's home clash with Manchester United but battled on until being substituted during the second period.
Sutton, 33, missed the Boxing Day trip to Tottenham but has now been advised by a neurosurgeon to rest for at least six weeks.
It is another major injury blow for Villa boss Martin O'Neill, who is already without the services of another striker, Luke Moore, with a long-term shoulder problem.
O'Neill said: 'Chris will be out for at least six weeks. He went to see the neurosurgeon who told him to rest and make sure everything is okay.
'He had blurred vision and concussion from early on in the game against Manchester United but played on.
'It is a big blow to us and to him. The prognosis is that things will get better but while he has got blurred vision he can't play.'
Sutton joined Villa on a short-term contract until the end of the season in late September and has gradually built up his fitness after a groin operation in the summer.
His goal against Everton secured Villa's only away win to date this season in the Premiership.
But now O'Neill has only Milan Baros, Juan Pablo Angel and Gabriel Agbonlahor at his disposal to play up front and he is certain to try and strengthen that department of the side in January.