Lacina Traore could face surgery to repair his damaged hamstring, Everton manager Roberto Martinez has confirmed.
The striker pulled out of Saturday's defeat at Chelsea and the Club are currently working closely with Monaco to determine the best possible treatment for the on-loan Ivorian.
Martinez said: "At the moment, it's too early to have a final answer on Traore because we don't know how long he's going to be out.
"I think it's important that we're working together with Monaco, because I think what we need to get right is that the player gets the perfect treatment.
"When I say the perfect treatment, this is not a straightforward injury. It's an injury that can be solved by a conservative treatment, or it can involve surgery - and I think that's a massive, massive decision.
"Depending what route we're going down, it's going to have certain consequences. It could mean that Lacina can play for us again or he can't.
“If it’s only going to be three or four weeks, we want him here. If it’s going to be anything longer than two or three months, clearly the loan period is over. It is going to depend how the conversations go today."
Traore joined the Blues from Monaco in January and made a goalscoring debut against Swansea City earlier this month.
And Martinez added: "Surgery can only be the resort if it's the right resort.
"That's something that at the moment we're exploring and making sure that, with the medical department of Monaco, we're getting all the information right.
"He is still a young man, but he is a sprinter. We need to make sure he's fully, fully fit for the years ahead in his career."