 On 23 May 2013, at Clontarf Cricket Club Ground, Dublin, he scored an unbeaten 84 in 47 balls against Pakistan which helped the Ireland to tie the match.Ireland required 15 runs in the last over to win the match, O'Brien hit last ball of Saeed Ajmal to boundary to pull out a thrilling 'tie' for the Irish team.O'Brien's performance at the World Cup attracted the attention of Gloucestershire County Cricket Club and he secured a contract with the club for 2011.