Michael Essien has returned to Chelsea from Real Madrid to have treatment on a mystery injury.
The midfielder is on a season-long loan at the Santiago Bernabeu, but this has been temporarily put on hold while Blues medical staff assess his condition.
Essien has been out for three weeks with what was believed to be a standard injury, although Real assistant boss Aitor Karanka suggested he had suffered an allergic reaction to medication.
The 29-year-old Ghanaian trained at Chelsea's Cobham headquarters on Friday.
Essien has made 10 appearances for Real Madrid this season, scoring one goal.