On 26 February 2017, he won a Leinster Colleges Championship medal after scoring a point from right wing-forward in a 1-14 to 0-13 defeat of Kilkenny CBS in the final.
[2] On 25 March 2017, Shefflin was switched to left corner-forward for the All-Ireland final against Our Lady's Secondary School from Templemore.
Shefflin joined the Ballyhale Shamrocks club at a young age and played in all grades at juvenile and underage levels.
[4] Shefflin again lined out at right wing-back when Ballyhale qualified to play Ballyboden St. Enda's in the Leinster final on 2 December 2018.
[6] On 27 October 2019, Holden lined out at full-back when Ballyhale Shamrocks faced James Stephens in the Kilkenny Championship final.
[8] On 18 January 2020, Holden made his fourth All-Ireland final appearance when Ballyhale Shamrocks faced Borris-Ileigh.