Everton striker Arouna Kone is set to have an operation on a knee cartilage problem which could rule him out of the rest of the season.
The Ivorian international was injured in the 2-1 win over Hull on 19 October and last week manager Roberto Martinez revealed it was more serious than first thought.
Everton have confirmed Kone, who turns 30 next week, will need surgery and although no timescale has been placed on Kone's recovery the club believe it will significantly impact the part the forward plays in the rest of the season.
"We had disappointing news (in that Kone) will need a bit of a period away," said Martinez. "We need to give him a lot of support because he was enjoying his role when he came on against Hull and then he got a nasty incident that is going to keep him away for a long time.
"He had a loosened body, a bit of cartilage in his knee, so we need to repair that which will take time. We're going to work on other aspects of his body to get him fully fit and strong so that when he comes back, he is ready to enjoy his football. It's going to be a long spell out and that's disappointing.
"We've got Darron Gibson reacting really well a couple of weeks after (knee) surgery so now he and Arouna are going to work extremely hard to get back before the season ends. We need to give them help and support on that side."
Martinez had more positive news regarding his in-form striker Romelu Lukaku, who received a knock in Sunday's goalless draw at home to Tottenham.
"We're very pleased with Romelu's recovery," he said. "We were a little worried on Monday but he reacted well to training and is fully fit to train, which is really good news. Everyone else has been fine - we didn't collect any other knocks or bruises on Sunday."