Roberto Martinez says Ross Barkley is already reacting well to treatment.
But it is still too soon to provide a specific return date for the England international.
Barkley missed Everton's game at Leicester on Saturday after suffering a knee injury in training.
Martinez is still waiting for swelling in the knee to go down so he can discover how long he will be without the powerful midfielder.
The Everton manager said: "His knee has reacted really well to treatment.
"I don't know where the figure of five months [in the papers] came from but obviously the extent of the injury is a little unsure at the moment because we don't know how the next two weeks are going to develop.
"It's a medial ligament injury and we know that Ross, in terms of the power and the strength that he has in his body, he could easily react to treatment a lot better than other players.
"The length that Ross will be out is a little uncertain at the moment and it could be anything between the eight weeks that we mentioned or a little further. Until the end of the week, or probably the next 10 days, we won't know how the knee is progressing and how quickly Ross can be back."
Barkley will undergo a further scan on his knee as the Everton medical team keenly monitor his recovery.
Martinez continued: "Obviously we are keeping an eye, very closely, on how that knee reacts and every time we have a real improvement we are checking that.
"At the moment his knee is in a brace and this is a very important period of rehabilitation, making sure that the ligament can be repaired in a good position. Obviously we are going to get further updates in days to come but we need to leave Ross alone and leave him to recover."
Martinez also confirmed that Darron Gibson wasn't involved at Leicester as part of the ongoing management of his return from injury.
But Seamus Coleman is now ready to start games and Arouna Kone and Bryan Oviedo are progressing well.
The manager added: "Darron is working really well and is building some better fitness levels. We need to make sure after a long spell on the sidelines that all the work we are doing is allowing him to be fully fit.
"It's going to be a very, very busy period in September and everything is working towards that month where Darron can be fully fit and he can have a really good period on the pitch, so it's not a problem at all with Darron.
"Arouna has already been working with the team and sometimes joining in with 11-a-side situations, which is very promising. But he still needs a bit of time to adapt to the physicality and the needs of the competition.
"Bryan is slowly getting stronger and he has already been reintroduced to the ball and into training with the group. We need to balance the right amount of work with the team with individual work to make sure that area is fully healed. It's still a bit early to be in a competitive phase, but not too far away.
"Seamus was fully fit from a medical point of view on Saturday and that was a real boost. He has been working really well, and he was desperate to be part of the squad on Saturday. I think now it's fair to say that he's considered fully fit and ready to join the group and help the team in any game."
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