Hernandez was perceived as having poor attitude issues because he sat out his entire senior year of high school due to a dispute with a coach. He played briefly at the College of San Mateo, a local community college, before he was drafted by the St. Louis Cardinals in the 41st round of the 1971 Major League Baseball draft as the 783rd player selected. He batted and threw left-handed, and through most of his career was listed as being 6' tall (1.83m) and 195 lbs. (88.5 kg).