O'Reilly played as a forward and was a freetaker for Dublin Hurling Team and his native club, Lucan Sarsfields.
O'Reilly won a Leinster Minor Hurling Championship medal for Dublin in 2005, with a five-point win over Wexford.
[2] During the same year O'Reilly won the Dublin Minor Hurling Championship with Lucan Sarsfields against Ballyboden St Endas.
O'Reilly played in the Leinster Under-21 Hurling Championship final in 2006, losing to Kilkenny GAA on a scoreline of 2-16 to 2-11 at Nowlan Park.
[5] He returned in for the first round of the championship in 2008 and played a major role in Lucan narrowly defeating their opponents by a point.