Walker moved to Wigan Athletic for an undisclosed transfer fee in January 2018. In August 2018 he joined Peterborough United on loan. He scored his first goal for Peterborough in an EFL Trophy tie against MK Dons on 4 September 2018. Walker was however recalled by Wigan on 2 January 2019 having made 18 appearances for Peterborough. Walker rejoined Hearts on 28 June 2019 on a three-year deal. He broke his leg in August 2019. He returned to first team training on the 28th of October. Walker has represented Scotland at U15, U16, U17, U19 and U21 level. Walker made his debut for the Scotland U21s against Luxembourg in a 3–0 win on 25 March 2013. In the game, he also scored his debut goal to make the score 1–0 with a volley from the edge of the box. Heart of Midlothian