Season of struggle
Club doctors are confident that the operation, on the cartilage in Mantorras's right knee, will cure a longstanding problem which has hindered the 20-year-old's progress this season.
Mantorras is expected to make a full recovery but could be out of action until February. The 2001 African young player of the year has scored three times in eight appearances for the Eagles this term. Benfica are in second place in the Super Liga, four points behind FC Porto.
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