Casey first came to prominence as a member of the Cork minor hurling team in the early 1980s. He won a Munster medal at this level in 1985, before later collecting an All-Ireland following a victory over Wexford. Three years later in 1988 Casey won a Munster title with the under-21 team. Once again he later collected an All-Ireland title following a defeat of Kilkenny.
By this stage Casey had made his senior debut in National Hurling League games. He made his championship debut against Waterford in 1989 and won his first Munster title in 1990 following a surprise victory over arch-rivals Tipperary. Cork later qualified for an All-Ireland final appearance with Galway. Like in previous meetings between the two sides Cork were complete underdogs, however, in a thrilling and high-scoring game Cork defeated the men from the West, giving Casey his first All-Ireland medal. He was presented with an All-Star award in 1991 and in 1992 he won a second Munster title. Cork later faced Kilkenny in the championship decider, however, victory went to ‘the Cats’ on that occasion. Casey added a National Hurling League medal to his collection in 1993. McCathy continued hurling at inter-county level until 1995.