Born in Motherwell, Devlin grew up in the same street as fellow footballerMark Reynolds and attended the same school, where the older pupil was held up as an example to follow. As a teenager Devlin spent time in the youth systems of Heart of Midlothian, Aberdeen and Celtic, making the squad for a Glasgow Cup final with the latter in May 2010 but being released soon afterwards. He was picked up by Hamilton Academical, with assurances that hard work would result in a swift path to first team football. He made his senior debut for Hamilton in the Scottish Premier League on 15 January 2011, aged 16, in a 0–4 defeat away at Rangers; the performance of Devlin and other young players in that match, including Lee Kilday who also made his debut, was praised by manager Billy Reid. He signed on loan for Stenhousemuir on 16 March 2011, and re-joined the Warriors on an emergency loan in February 2012, at the same time signing a two-year contract extension with Hamilton. He scored his first goal for the Accies in the Scottish Cup in December 2012. In February 2014, he signed a contract extension until the end of the 2014–15 season. In August 2016 he was appointed the club's new captain. In May 2017, he was involved in an altercation with a fan following a 1–0 home Lanarkshire derby defeat to relegation rivals Motherwell. In the last regular game of the 2016–17 season, Devlin suffered a serious knee injury, meaning he missed the club's two relegation play-off matches.
Aberdeen
Devlin moved to Aberdeen in January 2018 for an undisclosed fee, despite having not yet fully recovered from the knee injury suffered in May 2017. He eventually made his competitive debut for Aberdeen on 26 July 2018, in the first leg of a Europa League tie against Burnley at Pittodrie Stadium.
International career
Devlin was included in the Scotland squad for the first time in October 2018. He was recalled in May 2019, one of five uncapped players to feature. He made his debut on 10 October 2019 in a Euro 2020 qualifier against Russia. He started the game and played the whole match as Scotland lost 0–4.
