*Club domestic league appearances and goals, correct as of 23:16, 22 December 2024 (UTC) ‡ National team caps and goals, correct as of 23:44, 14 November 2024 (UTC)
On 4 July, Debast signed a five-year contract with Primeira Liga side Sporting CP, for a fee of €15.5 million, plus €5.5 million in add-ons, and a 15% sell-on clause in favor of Anderlecht.[7][8]
On 7 August, he made his debut for the club, where he committed two errors, that led to rivalsPorto first and second goals in their 4–3 loss in the 2024 Supertaça Cândido de Oliveira.[9] This resulted in him losing his starting spot, however, on 17 September with regular starter Eduardo Quaresma being sidelined with a knee injury, Debast was entrusted back to the starting eleven, scoring his first goal for the club, and the first goal of his career, by netting a shot from outside the box in Sporting's 2–0 victory over Lille during the inaugural matchday of the newly formatted Champions League league phase.[10]