 He impressed enough to win the Young Player of the Year at the club in 2004.O'Brien then signed for bitter rivals Bohemians for the 2005 season and he made his debut for Bohs against his former club Shamrock Rovers on 18 March 2005 at Dalymount Park.He never showed the same form at Bohemians and midway through the 2006 season, he returned to Shamrock Rovers on loan where he helped the Hoops to the First Division title.