Sergio Ramos: Pinchazo en la parte mosterior del muslo, isquios. Pendiente de evolución y de pruebas mañana.— Lucas Navarrete (@LucasNavarreteM) February 4, 2015
That doesn't say much, but it is all the available information at the moment. It means that Ramos had a problem on his hamstring and is awaiting for tests and development of the injury, meaning that he will probably have to miss Saturday's Derby against Atleti too. This injury probably means that Ramos will be out for a couple of weeks, although Real's medical staff will surely try to make it shorter for him to be back as soon as possible, depending of the development of the injury.
UPDATE on Ramos via @LucasNavarreteM: Hamstring problem, awaiting tests tomorrow and development of the injury.— Managing Madrid (@managingmadrid) February 4, 2015