On 4 July 2019, Devlin signed a two-year deal with the Wellington Phoenix after turning down a contract to stay with Sydney.[4] In his first few months, Devlin only made sporadic appearances off the bench alongside two appearances for the reserve team.
On 14 December 2019, following an injury to regular midfielder Alex Rufer, Devlin made his starting debut for the Phoenix in a 0–0 draw with Melbourne Victory; he quickly became an integral player for the team, being named A-League Player of the Month for December and retaining his starting spot even when Rufer recovered.[5]
Heart of Midlothian
On 28 June 2021, it was announced that Devlin had signed a two-year deal with the Newcastle Jets.[6] However, by August 2021 a transfer fee had been agreed with the Jets for Devlin to join Scottish Premiership club Heart of Midlothian, subject to the player securing a United Kingdom visa,[7] which he did on 24 August.[8]
Devlin made one appearance at the 2020 Olympic Games, coming on as a late substitute as Australia lost 2–0 to Egypt.[12]
Senior
Devlin was called up to the Australian senior side for the first time in September 2022 for two friendly matches against New Zealand in the leadup to the 2022 FIFA World Cup.[13] He came on for his senior international debut as a second-half substitute in the second game on 25 September 2022, in Auckland.[14]
On 8 November 2022, it was announced that Devlin was included in the Australian squad for the 2022 FIFA World Cup in Qatar.[15] Devlin did not take the field in the tournament for Australia, who were eliminated by Argentina in the round of sixteen.[16]