On 23 July 2018, according to the "Hamburger Morgenpost", Papadopoulos was suffering from a knee cartilage injury which required immediate surgical treatment. The rehabilitation period was estimated at six months, meaning he would will be able to compete again around Christmas, missing at least the first half of the 2018–19 2. Bundesliga season. On 30 March 2019, he returned to the squad as a substitute in the bench, in an away 0–0 game against VfL Bochum after a difficult recovery process (154 days to be exact) from his cartilage damage and three days later he made his debut with the first team as a starter in a 2–0 away win DFB Pokal game against Paderborn.