Liddle started his footballing career with Haydon Bridge and Sunderland, whom he joined as a youth player. At Sunderland he progressed through the youth side, until he was given a professional contract ahead of the 2008–09 season. It took until January 2010 for him to make his first-team debut in a FA Cup third-round match at home to Barrow; he came on as a substitute late in the game which Sunderland won 3–0.
On 14 November 2008 he secured a loan deal at Carlisle United, where he joined up with Graham Kavanagh, who was also on loan at Carlisle from Sunderland. His debut for the Cumbrians came the following day; he started against Brighton & Hove Albion as Carlisle United won 3–1. The loan was first extended until 14 February 2009, and then to the end of the season, where he went on to make twenty-two appearance.
On 5 August 2010, Liddle signed a four-month loan deal with Leyton Orient, but returned to Sunderland after only a month because of a groin injury he suffered on his only appearance, against Yeovil Town.
On 6 January 2011, Liddle joined Gateshead on a 28-day loan. He made his debut for Gateshead two days later, scoring his first senior goal in a 2–2 draw against Kidderminster Harriers, which was voted Gateshead's goal of the season. His loan deal was extended to the end of the 2010–11 season.
Liddle joined League Two club Accrington Stanley on loan for an initial month on 24 February 2012, and made his debut the next day in a 2–0 loss against Swindon Town. He was sent off against Southend United on 10 March, and initially was sent back to parent club Sunderland. However, after a defensive injury crisis, he returned to Stanley on loan until the end of the season.
On 18 July 2012, Liddle signed a one-year permanent deal for Accrington Stanley for an undisclosed fee. He began the season in the starting eleven for the first round of the League Cup, as Stanley lost 1–0 to his former club, Carlisle United, and kept his place for the opening league, a 1–0 win over Southend United. Liddle was sent off, for the second time in his Stanley career, in a 4–3 defeat to Chesterfield on 18 September. After the match, Liddle then served his three match ban. Later in the season, Liddle would be often used in first team ins and out in his first season, having spent time on the bench, in numbers of games and resulting him making thirty-six appearance in all competitions.
On 14 June 2013, Liddle signed a new one-year contract with the club ahead of the 2013–14 season. Liddle appeared in the first five matches to the start of the season before suffering from an injury that kept him out for two months. Liddle made his return to the first team on 2 November 2013 against Wycombe Wanderers, where he came on as a late substitute, in a 1-1 draw. Despite suffering from another injury, which was a hamstring problem and spent the most of the season on the substitute towards the end of the season, restricting him to making twenty-two appearance in all competitions.
On 1 July 2014, he signed another one-year contract extension with the club ahead of the 2014-15 season. Liddle appeared once at the start of the season, which was against Southend United in the opening game of the season, which saw them lose 1-0. However, Liddle suffered an injury that kept him out of months. It wasn't until on 9 November 2014 when he made his first team return, in the first round, with a 0-0 draw against Notts County. After the match, Liddle's performance named him Man of the Match. However, Liddle's appearance was soon restricted, as he was demoted to substitute bench for the most of the season and went on to make nineteen appearances in all competitions.
At the end of the 2014-15 season, Liddle were among three players to be released by the club, ending his three years spell there.
After leaving Accrington Stanley, Liddle went on trial at Scottish side Hibernian. However, he failed to win a contract at Hibernian after suffering a knee injury during the development match and the club vowed to help him overcome the injury.
After a spell with EBAC Northern League side Dunston UTS, Liddle joined Northern Premier League side Blyth Spartans in June 2016. Liddle made his Blyth Spartans debut in the opening game of the season, in a 3-1 win over Coalville Town.
Liddle, although born in England, qualifies to play for Ireland due to his Irish mother. After playing in the under-18s and under-19s for his country, Liddle was called up to Ireland's under-21 squad for a friendly against Austria under-21 on 19 August 2008. At this stage he had not made an appearance for his club after being signed on a professional contract in the 2008–09 season. Sunderland manager, Roy Keane, commented that "The young players have done well. It's a real plus for us and I have no doubts that some of them will be able to handle it at the top level". He started against Austria, in a 1–1 draw, Liddle expressed his surprise after the call up, saying "The call-up came as a big surprise. I didn't expect it. When I was named in the starting eleven I [sic] buzzing!" He made further appearances against Bulgaria, Portugal, Lithuania and Germany.As of match played 16 November 2013.