Deasy joined the Ballyea club at a young age and played in all grades at juvenile and underage levels, enjoying championship success in the under-21 grade in 2012. On 30 October2016, Deasy scored 1-03 from right wing-forward when Ballyea defeated Clonlara by 2-14 to 1-14 to win the Clare Senior Championshipfor the first time ever. He retained his place at wing-forward for the subsequent Munster Championship, which culminated with him winning a provincial medal after a 1-21 to 2-10 defeat of Glen Rovers in the final. On 17 March 2017, Deasy scored 1-06 when Ballyea were defeated by Cuala in the All-Ireland final. On 21October 2018, Deasy won a second Clare Championship medal following Ballyea's 1-20 to 1-14 defeat of Cratloe in the final. He ended the championship as the top scorer with 2-48.
Clare
Minor and under-21
Deasy first played for Clare at minor level in 2011. He was an unused substitute throughout the championship campaign, which culminated with the winning of a Munster Championship medal on 10 July 2011 after a 1-20 to 3-09 defeat of Waterford in the final. Deasy subsequently joined the Clare under-21 hurling team and won a Munster Championship medal as a non-playing substitute on 30 July 2014 after a 1-28 to 1-13 defeat of Cork in the final. On 13 September2014, Deasy was also an unused substitute in Clare's 2-20 to 3-11 defeat of Wexford in the All-Ireland final.
Senior
Deasy was added to the Clare senior hurling panel in late 2016. His involvement with the team during the National Hurling League was curtailed because of his involvement with the Ballyea club team and he was an unused substitute during the subsequent championship campaign. Deasy made his first appearance for the Clare senior hurling team on 19 February 2017 in a 2-18 to 1-18 defeat by Kilkenny in the National Hurling League. Later that season he made his first championship appearance, scoring 1-01 from play, in a 3-17 to 2-16 defeat by Clare in the Munster Championship. Later that season he made his first championship appearance, coming on as a substitute for David Reidy, in a 2-27 to 2-18 defeat of Waterford in the Munster Championship.
