Must watch my DVD of EL CID (1961) again. Sagrajas is mentioned but not portrayed.
As I recall in the movie, The Cid refuses to join Alphonso at Sagrajas because he and his Moorish allies (who were fighting on Spain's side) did not deem it practicable. Alphonso proceeded without the Cid and his allies and got creamed. Not sure if there is any historical accuracy in El Cid, but I love the movie.