Born in Villamayor de Calatrava, province of Ciudad Real, Casimiro had a very short career as a basketball player.

In 1993, Casimiro managed Gandía BA, of the Spanish second-tier level, in his first professional experience as a head coach.

Five years later, Casimiro managed TDK Manresa to win the 1997–98 Liga ACB, which is considered to be one of the biggest miracles in the history of Spanish professional club basketball.

[1] After leaving Manresa, Casimiro continued coaching in Spain, in different teams of the Liga ACB and LEB Oro.

Three years later, he managed Baloncesto Fuenlabrada to achieve a league promotion to the Liga ACB, by winning the 2004–05 LEB.