Career
O'Brien, who plays as a winger, has represented the Republic of Ireland at full international level five times, all while he was on the books of Newcastle United. Newcastle United
O'Brien played for Cabinteely and St Josephs at youth level in Ireland before signing for Newcastle United. He played in the under–17 national championship winning team who beat Manchester United 5–2 in a final played over two legs at Old Trafford and St James' Park.
He then featured regularly for the Newcastle reserve team during the 2003/04 season, but he suffered a broken leg in a training ground accident in July 2004. O'Brien progressed in the next year to the extent that he was in the first team squad, but he was sent on loan to Carlisle United during October 2005. He scored within 10 minutes of his debut for Carlisle, but the loan spell was cut short due to injury.
Wolves and Norwich City were interested in signing O'Brien, but Glenn Roeder kept O'Brien due to the demands on a small Newcastle squad. O'Brien eventually made his first full Premier League appearance on 20 January 2007 against West Ham United at St James' Park. He played the full 90 minutes against West Ham, but never made another first team start.
Hibernian
On 25 June 2007, O'Brien agreed to sign a three-year contract with Scottish Premier League side Hibernian after the expiry of his contract with Newcastle United, who were entitled to compensation. He played more regularly for Hibs during the 2008–09 season, although he missed two months due to a knee injury. He was released by the club on 1 July 2009 after his contract was cancelled by mutual consent.
Swindon Town
Soon after his release by Hibernian, O'Brien signed for Swindon Town. He made his debut for Swindon on the opening day of the 2009–10 season in a 5–0 defeat away at Gillingham. O'Brien managed four appearances for Swindon before suffering a hamstring injury in August.
O'Brien made just one substitute appearance under the management of Paul Hart, who decided to release O'Brien from his contract in April 2011. O'Brien made a total of 40 appearances, the majority as a substitute, in two seasons for Swindon. Yeovil Town
O'Brien signed for Yeovil Town on 12 August 2011.
He was released from his contract by Yeovil on 4 January 2012, along with Kerrea Gilbert, Flavien Belson and Abdulai Bell-Baggie. Gateshead
O'Brien signed for Gateshead on 9 February 2012. He made his debut on 18 February 2012 in a 2–1 defeat against Forest Green Rovers.
O'Brien was released by Gateshead at the end of the season. Hungerford Town
O'Brien was capped by Ireland at several youth levels. After impressing during the pre-season of 2006 he received a call up to the senior squad for the first time, where he joined up with then Newcastle teammates Damien Duff, Stephen Carr, and Shay Given.
He came on as a second-half substitute for the friendly match against Netherlands to gain his first full international cap.
