Joey O'Brien

2.1. Bolton Wanderers

O'Brien officially began his professional career with Bolton Wanderers in 2004, having progressed through their youth ranks since 2002. To gain crucial first-team experience, he was loaned to Football League One side Sheffield Wednesday for a substantial part of the 2004-05 season. During this loan spell, he made 15 appearances and scored two goals, including a memorable debut goal. His contributions were highly regarded, leading to his loan being extended twice. In recognition of his impact, he was given the captain's armband for his final game before returning to Bolton.

Upon his return to Bolton, O'Brien made his Premier League debut on 15 May 2005 as a late substitute against Everton. He earned his first start for Bolton in September 2005 in a UEFA Cup first-round match against PFC Lokomotiv Plovdiv. During the 2005-06 season, he solidified his place in the first team, making 33 appearances across all competitions, stepping up during a period of defensive injuries. Initially playing as a central midfielder, O'Brien transitioned to a right-back role where he made a strong impression, with manager Sam Allardyce describing him as a "dominant force at right back in the Premiership."

The 2006-07 season was severely affected by a knee injury, which sidelined him for most of the campaign. Despite initially being expected to return within a month, his recovery was prolonged for several more months. He eventually made his return to the Bolton squad on 23 September 2007, starting in a 1-0 victory over Tottenham Hotspur. For most of the 2007-08 season, O'Brien played in his more natural midfield position, making 26 appearances despite facing further injury concerns.

In July 2008, he was assigned the number 8 shirt, previously worn by Iván Campo, and started the 2008-09 season strongly by providing two assists against Stoke City and Arsenal. However, persistent injuries once again limited him to just eight appearances throughout that season. The 2009-10 season proved even more challenging, as he made no appearances due to another knee injury that required surgery. Despite this setback, the club demonstrated faith in him by offering a one-year contract extension, keeping him at Bolton until the summer of 2011. Although he recovered and played in a pre-season friendly in 2010, he never rejoined the first team.

On 24 March 2011, O'Brien rejoined Sheffield Wednesday for a second loan spell, remaining with them until the end of the season. He made his second debut for the club two days later in a 1-1 draw against Dagenham & Redbridge, ultimately making four appearances. At the end of the 2010-11 season, O'Brien was released by Bolton Wanderers, concluding his six-year association with the club. In August 2017, he briefly returned to Bolton to train with the club's fitness coach, Nick Allamby, to maintain his physical condition.

2.2. West Ham United

In July 2011, O'Brien was given a trial by West Ham United, participating in pre-season friendlies against BSC Young Boys and Basel. He impressed sufficiently to sign a two-year contract on 30 July on a free transfer.

O'Brien made his competitive debut for West Ham on 7 August 2011 in a 1-0 home defeat to Cardiff City. He scored his first goal for the club, and his first since January 2005, in a 4-0 away victory against Watford on 16 August 2011. On 10 December 2011, he received the first red card of his career in an away match against Reading. Despite contending with injuries during the season, O'Brien made 33 appearances across all competitions as West Ham secured promotion back to the Premier League.

For the 2012-13 Premier League season, O'Brien initially suffered a hamstring injury on 5 October 2012 but returned to the squad within three weeks for a match against Wigan Athletic. Shortly after his return, he assisted Kevin Nolan's winning goal in a 1-0 victory over Newcastle United. His contributions continued with his first-ever Premier League goal on 19 November 2012, which secured a point against Stoke. He then scored the winning goal in West Ham's New Year's Day fixture against Norwich City. On 13 January 2013, O'Brien signed a new contract with West Ham, extending his stay until 2016. He returned from another hamstring injury on 19 January 2013, playing in a 1-1 draw against Queens Park Rangers. He concluded the 2012-13 season with 34 appearances in all competitions.

In the 2013-14 season, O'Brien's appearances were limited to 17. After missing two matches in January 2014 due to injury, he returned on 29 January 2014, starting and playing the full game in a 0-0 draw against Chelsea. However, during this match, he suffered a dislocated shoulder after an "off-the-ball push from Chelsea defender Gary Cahill", which sidelined him for three months. He made his return in late April for the final game of the season, playing as a right-back in a 2-0 loss against Manchester City.

The 2014-15 season saw O'Brien feature in the first three matches before suffering a knee injury during an international break. After his return as an unused substitute against Burnley on 18 October 2014, he struggled to regain his starting position, spending most of the season on the bench due to the strong performances of Carl Jenkinson.

Ahead of the 2015-16 season, O'Brien was expected to compete for a first-team place under the new manager Slaven Bilić. He made five appearances in West Ham's UEFA Europa League campaign before suffering a calf injury at the start of the domestic season. After returning from this injury in late October, O'Brien made his first appearance on 30 January 2016 in the fourth round of the FA Cup, a 0-0 draw against Liverpool. He also played in the FA Cup replay against Liverpool, which West Ham won 2-1. Following this match, he sustained yet another hamstring injury, which kept him out for the remainder of the 2015-16 season, preventing him from making any further appearances. He was subsequently released by West Ham at the expiration of his contract in June 2016.

2.3. Shamrock Rovers

After being without a club for 18 months, O'Brien signed with League of Ireland team and his boyhood club, Shamrock Rovers, on 27 January 2018. He spent his final professional playing years with the club, ultimately retiring there.