The 34-year-old missed out as Los Blancos collapsed to a 3-2 defeat at home to Shakhtar Donetsk in their Champions League opener on Wednesday night, having sustained a knock during last weekend's loss to Cadiz, which also came at their temporary Estadio Alfredo Di Stefano home.
Ramos was one of four players taken off at half time of that defeat to Cadiz and he now faces a race against time to be fit for Saturday's game against bitter rivals Barcelona.
The defensive stalwart has been training alone since picking up the knock and will undergo a late fitness test to determine whether he is ready for the visit to Camp Nou.
Both Madrid and Barca go into Saturday's match off the back of domestic defeats last weekend, although Barcelona returned to winning ways in the Champions League on Tuesday. body check tags ::