Atletico Madrid defender Javier Manquillo was diagnosed with whiplash after a heavy fall against Real Madrid.
Manquillo was injured shortly before half time after an aerial altercation with Cristiano Ronaldo, who was booked for his challenge.
The full-back player landed awkwardly on his head and neck and was substituted at half time.
Marca reports that Manquillo underwent a number of tests at a local hospital and will remain under observation after the procedures revealed he suffered whiplash.
Ronaldo, who was struck by a lighter thrown from the crowd as he left the pitch at half time, is said to have been in contact with Manquillo and wished him a speedy recovery.