Career
A Manchester United youth graduate, O'Brien made his senior debuts with Glossop North End in 2009. He joined Northwich Victoria in the 2010 summer, but was deemed suplus to requirements in January 2011. O'Brien was loaned to Radcliffe Borough in February 2011.
After appearing regularly he moved to Mossley in August 2011. He made 60 appearances for the club before joining Chorley in December 2012, for an undisclosed fee. He was also named in the campaign's Team of the Year.
On 19 June 2014 O'Brien signed a two-year deal with League Two side Bury. However, he suffered a knee injury in September, being sidelined for a few months. On 21 October of the following year he was loaned to Halifax Town, until 9 January.