Dublin-born defender Mark O’Brien has already experienced plenty of highs and lows during his fledgling career.
O’Brien is regarded as an ‘old fashioned centre-back’ who is brave, determined and focused on his job for the team, and he made his first-team bow as a second-half substitute in the 3-1 defeat at Watford on the final day of the 2008/09 campaign at the age of 16; soon after being named as the club's Academy Player of the Year.
In October 2009, O’Brien underwent surgery to repair a valve in his heart, but he resumed full training a few months later and spent 2010/11 as a regular for the Under-18s.
2011/12 saw him become a full-time professional and he made his first-ever career start in the second game of the season, before going on to forge a solid defensive partnership with Jason Shackell, only for a cruciate ligament injury to bring a premature end to his season in December 2011.
He returned to action during the 2012/13 campaign before suffering another knee injury in February 2013 that ruled him out for the final three months of the campaign, after undergoing surgery.
The 2013/14 season was equally frustrating for O’Brien, who returned to full fitness but was unable to dislodge Richard Keogh and Jake Buxton at the heart of the Rams’ defence and he failed to make a first-team appearance, although he was a regular in the Club’s Under 21 side.