EXCLUSIVE | By Chelsea correspondent Tony Hughes

Thibaut Courtois has suffered a knee injury that is expected to keep him out for three months, Football Insider sources understand.

The Chelsea goalkeeper broke down in training on Wednesday with the problem and was immediately ruled out of Saturday’s trip to Everton.

The swelling on the knee initially prevented Chelsea medics from taking a scan to assess the full extent of the injury, but he has now seen a specialist.

Sources have told Football Insider that Chelsea have learned the Courtois injury is severe enough to sideline the Belgium international for up to three months.

To lose his No1 goalkeeper is a huge blow to manager Jose Mourinho and comes in the wake of the team’s shaky start to the season, in which they have won just one of their first four league matches.

Asmir Begovic, who moved to Stamford Bridge from Stoke for £8million in the summer, will stand in for Courtois at Goodison Park and during the 23-year-old’s absence.

Begovic is a capable deputy but Courtois has established himself as one of the world’s outstanding goalkeepers both at Chelsea and at former club Atletico Madrid, where he had a very successful loan spell.