In November and December 2014, Liddle played for the Australian Schoolboys. In 2015 and 2016, he played for the Wests Tigers' NYC team, and he was named the team's Player's Player in 2015. He played for the New South Wales under-20s team against the Queensland under-20s team in 2015, and was selected again in 2016, but forwent the match to make his first-grade debut.
2016
On 14 June, Liddle re-signed with the Tigers on a 2-year contract until the end of 2018. With Robbie Farah absent for State of Origin, and Manaia Cherrington and Matt Ballin injured, Wests Tigers were given a dispensation for Liddle to make his debut in round 18 against the Canterbury-Bankstown Bulldogs, despite exceeding the 2nd tier salary cap. Coming off the bench, he scored a try early in the 2nd half. Coach Jason Taylor said, "For salary cap reasons he probably won't play any more part. That's disappointing. He didn't look out of place for a second against a team with those big guys and his defence was superb."
2017
With Farah leaving the club, Liddle was a regular in first grade, mostly playing from the bench and interchanging with Matt McIlwrick at hooker. From round 16, he changed to the starting hooker, but 3 games later he suffered a season-ending shoulder injury. Scoring 3 tries from his 13 appearances, Liddle was awarded the Wests Tigers Rookie of the Year. Mid-season he signed an extension to remain at the club to the end of 2019.
2018
Returning from his shoulder injury, Liddle played on the bench in round 4. He said, "Definitely long-term, I want to wear that No.9 jersey. I think at the moment I just want to keep on playing footy and getting my match fitness up and getting my tackling right. But I was pretty happy with the hit out today." He made his return to the starting team in round 6, and scored a penalty try against the Manly Warringah Sea Eagles, after he was illegally tackled without the ball by Daly Cherry-Evans, causing him to fumble the grounding of the ball. The Tigers went on to win 38-12. Injury again limited Liddle in 2018, making 13 appearances with only two in the starting side. With former captain Robbie Farah returning to the club mid-season, all of Liddle's subsequent appearances were spelling Farah. Liddle said, "He's come back and showed me a few things. I watch him at training on the field and you learn off him. I probably haven't played as much as I've wanted to play this year, but it's all a learning process."
2019
Liddle remained the second string hooker behind Farah in 2019. After missing the beginning of the season with rehabilitation, he played 10 games off the bench mid-season before returning to reserve grade. With Farah suffering an injury in round 21, Liddle was recalled as starting hooker in round 22, but was taken from the field with a serious knee injury after just six minutes of play. He was ruled out for the remainder of the season with a torn anterior cruciate ligament, saying, "I’ll come back bigger and stronger. I’ve had two shoulder recos and you just take it day by day. You don’t think about the long haul, you just think about the daily things, doing the recovery. It’s all mental really. You get back on the horse and plough ahead."
