Everton boss David Moyes concedes there is a chance Victor Anichebe could miss the rest of the season.
Anichebe suffered a knee injury in last weekend's 0-0 draw at Newcastle United following a shocking challenge by Kevin Nolan.
The striker has damaged ligaments in his knee, but the Toffees are waiting for the swelling to subside in order to learn the full extent of the damage.
Moyes admits Anichebe could be sidelined for up to month, if the injury proves to be only strained ligaments in the knee.
However, the Everton chief also acknowledged that a more serious diagnosis would likely see the powerful forward sit out the remainder of the campaign.
"Victor has got a bad injury from the tackle," said Moyes.
"He has lateral knee ligament damage, and possibly some other damage as well which we won't be able to clear up until next week.
"But at the moment, if it's what we think we have now then it will be three to four weeks, if not then he could be out for the rest of the season."
Everton are already without fellow strikers Yakubu and James Vaughan, while Mikel Arteta is out for the rest of the season after also suffering a knee injury at Newcastle.