Real Madrid Castilla starlet Marcos Alonso was called into the senior squad by coach Manuel Pellegrini for their victory over Valencia.
Alonso was put on notice over doubts surrounding the availability of Marcelo.
Marcos Alonso, 19, is the son of former Barcelona and Atletico Madrid star Marcos Alonso Snr and the grandson of Real Madrid legend Marquitos, a five-time European champion with the club.