Chelsea manager Jose Mourinho has confirmed Thibaut Courtois requires surgery on a knee injury and will be out for "quite a long time."
There have been mixed reports on how long goalkeeper Courtois will be sidelined after he sustained the problem upon his return to training with Chelsea following the international break.
ESPN FC sources have said he will be unavailable for selection for 10 to 12 weeks, with the timescale set to be confirmed by the club later on Friday.
Mourinho said at a news conference ahead of Saturday's meeting with Everton: "Courtois was injured in a training session with the goalkeepers and I cannot tell you much, but I can tell you that he needs surgery in his right knee.
"As a consequence of that he will be out for quite a long time. I cannot be at this moment more specific about the injury or the time he will be out."
- BelgianRedDevils (@BelRedDevils) September 11, 2015
Asmir Begovic, who signed for Chelsea from Stoke in the summer, is set to deputise for Courtois, having already featured in his place when he was suspended for the 3-0 loss at Manchester City.
Chelsea have endured a poor start to the defence of their Premier League title, winning one and losing two of their opening four matches.