Inter-county O'Riordan made his senior championship debut for Cork on 9 June 1946 in a 2-9 to 2-1 Munster quarter-final defeat of
Clare. He immediately became a regular member of the starting fifteen and later won his first
Munster medal following a 3-8 to 1-3 defeat of
Limerick. On 1 September 1946 Cork faced old rivals
Kilkenny in the All-Ireland decider. While some had written off Cork's chances, they took an interval lead of four points. With ten minutes remaining Cork's lead was reduced to just two points, however, goals by O'Riordan and
Joe Kelly secured a 7-6 to 3-8 victory. It was O'Riordan's first
All-Ireland medal. Cork retained their provincial dominance in 1947 with O'Riordan picking up a second winners' medal following a 2-6 to 2-3 defeat of Limerick once again. The subsequent All-Ireland final on 7 September 1947 was a repeat of the previous year with Kilkenny providing the opposition. The stakes were high for both sides as Cork were aiming for a record sixth championship in seven seasons while Kilkenny were aiming to avoid becoming the first team to lose three consecutive All-Ireland finals. In what has been described as one of the greatest deciders of all-time, little separated the two teams over the course if the hour. A Joe Kelly goal put Cork one point ahead with time almost up, however,
Terry Leahy proved to be the hero of the day. He converted a free to level the sides again before sending over the match-winner from the subsequent puck-out. With that the game was over and Cork were beaten by 0-14 to 2-7. It was the fifth time that Kilkenny had pipped Cork by a single point in an All-Ireland final. After a period of dominance by
Tipperary between 1949 and 1951, Cork bounced back in 1952. A late
Paddy Barry goal gave Cork a 1-11 to 2-6 defeat of four-in-a-row hopefuls Tipperary. It was O'Riordan's second Munster medal. On 7 September 1952 Cork faced
Dublin in the All-Ireland decider. An appendicitis ruled
Joe Hartnett out of the game, resulting in
Willie John Daly being switched to centre-forward.
Liam Dowling scored a vital goal in the first half to give Cork the interval lead. Dublin's attack collapsed in the second half as Dowling scored a second goal. The 2-14 to 0-7 victory gave O'Riordan his second All-Ireland medal. ==Biography==