John was one of the outstanding young talents to emerge in the Dunshaughlin club during the 1960's. He was a key player as the Black and Amber gained Meath junior championship honours in 1967, Athboy were beaten in the A final while Junior B winners Skryne were overcome in the final proper. Amongst John's team mates was Noel Curran who also starred as Meath gained All-Ireland senior honours that same season. 

Indeed, many good judges of this era rated John Casey good enough to play regularly for the Meath seniors himself, a feat he did achieve, also in 1967 when lining outas a midfielder for Meath against Kildare at the opening of the Dunshaughlin grounds. He was still highly involved in 1968 when Dunshaughlin had to play Dunderry on no less than four different occasions in an epic series of intermediate championship games. John was also an exceptional handball player and in 1972, alongside Paddy Burke, the pair won the Meath Senior Double's for teh Dunshaughlin club.