 He was one of the eleven cricketers to play in Ireland's first ever Test match, against Pakistan, in May 2018, scoring the first Test century for Ireland men's cricket and becoming the first sportsperson from Ireland to represent his country 300 times.O'Brien is an aggressive right-handed middle to lower order batsman and a right-arm medium-fast bowler.He made his One Day International (ODI) debut in 2006 in Ireland's inaugural match.