On 25 September 2019, Costa made his first-team debut in the opening group match of the Taça da Liga, keeping a clean sheet in a 1–0 home victory over C.D. Santa Clara. His first Primeira Liga appearance took place on 10 November in a 1–0 away defeat of Boavista FC, as the habitual starter Agustín Marchesín was suspended internally after a breach of discipline. He made a further two until the end of the campaign for the eventual champions.