Liddle was born in Middlesbrough, North Yorkshire. He began his career with hometown side Middlesbrough. He was a regular in the academy sides and won the 2003–04 FA Youth Cup. He signed a professional contract with Middlesbrough on 14 July 2003.
Hartlepool United
In August 2006, Liddle joined nearby League Two club Hartlepool United. On 13 August 2011, while playing in a home league match against Walsall, Liddle suffered an injury, as his zygomatic bone became fractured in two places. He was able to complete the match, which ended in a 1–1 draw. However, he was sidelined afterwards. For his return to playing, he wore a protective mask. On 19 May 2012, it was announced that Liddle was released from Hartlepool United after six years.
Liddle signed for League One club Notts County on 21 June 2012 on a two-year contract. Liddle stated that it was Keith Curle's desire to manage in the Championship that played a big part in the switch. "Keith wants to manage in the Championship with Notts. That's why I came here. Hopefully I can help him do that". Before the start of the 2012–13 season, Liddle admitted there was a challenge to earn a first team spot. "It's the most competitive squad I've ever been in, If I get the shirt I will have to play well to keep it and if I'm not in the team I'll have to work even harder in training to get in there." He made his competitive debut for the club in a 2–1 victory over Crewe Alexandra, partnering Dean Leacock in the centre of defence. Liddle made a good start to his career at Notts County and was awarded the PFA Fans' Player of the Month for September, continuing to play at centre back, he ensured County remained unbeaten in that month. Liddle made his final and 46th league appearance of the season against Coventry City. It meant he had played every minute of the 2012–13 season, equalling a record last set by County's Pedro Richards 30 years ago. He then won four awards at the clubs' end of season award ceremony. Including; The Manager's Player of the Year, Players' Player of the Year, Fans' Player of the Year and the Supporters' Club Player of the Year.
Liddle signed for Bradford City on 9 June 2014 on a one-year contract with the option of an additional year. He made his debut on 9 August 2016 in a 3–2 home win against Coventry City.
Liddle signed for Chesterfield on 1 February 2016 for an undisclosed fee. He was named the club's captain. Liddle was sent off in his third appearance for the 'Spireites', on 16 February 2016 in an away game to Colchester United for an 18th minute foul. Liddle scored his first goal for the club on 13 August 2016, scoring the first in a 3–1 victory over Swindon Town, heading into an empty net after a Ched Evans free kick was saved.
Liddle signed for League Two club Carlisle United on 13 January 2017 on a one-and-half-year contract for an undisclosed fee. He was released by Carlisle at the end of the 2018–19 season.
Hartlepool United
Liddle resigned for Hartlepool permanently for a second time after a successful loan spell in the previous season from Walsall.
