Diego Costa has been diagnosed with a cervical disc herniation in a fresh blow to goal-shy Atletico Madrid.
Scans undertaken in recent days identified the issue, which relates to the spine, but a rehabilitation programme has not yet been formulated.
Atletico said the 31-year-old requires special neurosurgery assessment before the full scale of the injury can be established.
Former Chelsea striker Costa trained earlier this week after appearing for the final 10 minutes of Atletico’s 3-1 win over Espanyol on Sunday.