Sevilla star Jesus Navas is facing a minimum of six weeks on the sidelines with a knee injury.
The skilful wideman picked up the complaint in Sevilla's 3-0 Copa del Rey victory over Gimnastica Segoviana on Wednesday night and it could yet prove more serious still.
The 20-year-old has undergone initial tests on his left knee which revealed meniscus damage, but swelling prevented medical staff from making a full diagnosis with ligament damage still a possibility.
Navas will have a further test on Friday to assess whether the ligaments have been affected - if they have his six-week lay-off will be significantly lengthened.
The news will come as a real blow to Sevilla boss Juande Ramos for whom Navas has been a virtual ever-present this term.
The youngster, who has been dogged by psychological problems in recent years, appeared to have put his off-field worries behind him this season and was fulfilling the rich potential he so obviously possesses.