Castillo will head to Florida Tech following two seasons at Jacksonville, where he appeared in 19 games over two seasons. In 2019, the infielder logged a .250 batting average with five RBIs and three runs scored over 24 at-bats. He also made three starts during the shortened 2020 season. Before Jacksonville, Castillo played two seasons at Eastern Florida State College, where he slashed .310/.351/.496 and earned second team All-Conference recognition. On the summer ball circuit, Castillo played for the Harrisonburg Turks of the Valley League in 2018, where he hit five home runs and drove in 20.