London - Chelsea manager Jose Mourinho says goalkeeper Thibaut Courtois has picked up a right knee injury that will require surgery and will keep him out of action for "quite a long time."
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Mourinho says the Belgium international picked up the injury in training, but adds that he could not be "more specific about the injury or the time he will be out."
Courtois' absence will mean a return for Asmir Begovic in goal for Saturday's match at Everton.
The injury is the latest setback for the Premier League champions, who have taken only four points from their opening four games and are already eight points adrift of leader Manchester City.
Mourinho also says Brazil midfielder Oscar is still unavailable because of injury.