Derby County
Green made his first appearance in a Derby shirt at home to his former club Doncaster Rovers in a 1–0 defeat on 9 August 2008. He scored his first goal for his new club away at Bristol City in a 1–1 draw on 19 August, and grabbed his second in a 1–0 League Cup win at Preston on 26 August. Green established himself well in the Derby side and was the clubs' only remaining ever-present when he played his fourteenth consecutive game, a 3–2 defeat to Blackpool on 21 October.
He played 40 out of Derby's first 45 fixtures, including both legs of Derby's League Cup semi-final against Manchester United, before breaking his fifth metatarsal whilst sprinting in a training session on 6 March 2009. He was predicted to be out for 6 to 8 weeks, and missed the remainder of the season. He finished the season with six goals in all competitions.
Green began the 2009–10 season well, playing in six of Derby's opening seven games, and scoring in Derby's 3–2 defeat to Scunthorpe United on 15 August 2009. However, he picked up a slight foot injury in the first game of the season, a 2–1 win over Peterborough United on 8 August. He continued to play through the injury with painkilling injections, and had appeared to be recovering. However, his start against Sheffield United on 12 September would prove to be his last appearance for almost two months as his foot injury flared up again. After having another operation on his foot on 18 September, Green was predicted to return to action in four weeks. However, Green suffered a setback in his recovery and his comeback was delayed until 6 November. Following his return, Derby's form improved and he helped The Rams to 8 wins and 5 draws in the next 18 games he played, scoring the equaliser in Derby's 2–1 win over Reading on 28 November. Whilst Derby's form did not hold, winning only 1 of their next 8 games, Green did hold his place in the first team for the remainder of the season, until he pulled a muscle in the warm-up for the penultimate game of the season at Bristol City which cut Green's season slightly short.
He finished the campaign with 2 goals from 37 appearances in all competitions. Green's performance, alongside his first international caps for the Republic of Ireland, attracted the interest of Celtic, though Derby quickly dismissed the rumours, describing Green as "untouchable." He signed a one-year extension to his contract in March 2010, to take him through until the end of the 2011–12 season.
Green started the opening nine league fixtures of Derby's 2010–11 campaign, only missing out in the League Cup due to an international call-up, and scored his first goal of the season in a 5–0 thumping of Crystal Palace on 25 September 2010. Although primarily playing as one of the three advanced midfielders behind a loan forward in Derby's new 4–2–3–1 formation, he moved to right back for a 3–1 victory over Middlesbrough as injuries left Derby short in defence. Despite Derby's inconsistent form, Green was almost an ever-present throughout the season and was linked with moves to the Premier League with Wolverhampton Wanderers and Blackpool
In the January 2011 transfer window, Green remained at Derby and remained a key figure in the side before picking up a cruciate and mediate ligaments injury in a 4–1 defeat at Cardiff City which ruled him out for the subsequent six to nine months.
As a result of his injury, Green missed the rest of the 2010–11 season and the first 16 games of the following season, returning to action in a reserve fixture against Sheffield United on 15 November 2011. He was allocated squad number 32 upon his return. Green made his first team return as a late substitute in a 2–0 defeat against Hull City on 19 November 2011, making his first start in a 3–1 defeat at West Ham United on 26 November. Green then became a regular starter, scoring in a 2–1 win at home to West Ham United on 31 December 2011, only missing the 3–2 defeat at Barnsley on 31 January 2012 and the final two games of the season at Portsmouth and home to Peterborough United. Green's contract ended in June 2012 and Derby were keen to extend this deal, with Rams manager Nigel Clough fearing being unable to agree terms with Green. Derby offered Green a new contract in April and gave Green until the end of the month to make a decision. Leeds United were reportedly interested in Green. On 20 April 2012, it was revealed that Green had rejected Derby's contract offer meaning the player would leave the club in the summer.
Derby manager Nigel Clough responded to the news by dropping Green for the matchday squad in the penultimate game against Portsmouth, with 17-year-old academy winger Will Hughes taking his place in the matchday squad. Green's departure was formally announced on 3 May 2012, Green said in an interview that he rejected Derby's contract offer because he thought it was time for a change.
