Arouna Kone faces a battle to feature before the end of the season after Roberto Martinez revealed the forward had suffered a cartilage problem.
The Ivory Coast international picked up a knock to his knee in the 2-1 win over Hull City and was set to undergo tests to further diagnose the injury.
The results of those disclosed Kone's injury as worse than first feared and Blues boss Martinez admits he will be without his striker for 'a long spell'.
He told evertontv: "We had disappointing news [by which Kone] will need a bit of a period away. 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 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 brighter news regarding another of his strikers, however, with the Spaniard hopeful Romelu Lukaku will be fit to face Crystal Palace on Saturday after sustaining a knock against 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 Saturday."
With the Merseyside derby sold out, the Blues are next in action at home against Stoke City on 30 November. Tickets can be purchased here or click here for hospitality.