Leysen, a 23-year-old defender, played in the youth academy of PSV. He moved to Union Saint-Gilloise in 2023, where he played 86 matches and helped the team win the championship. Leysen previously played for Jong PSV, making 53 official appearances for the team.
Leysen started his youth development at Westerlo and OH Leuven before moving to PSV in 2017. He progressed through various youth teams in Eindhoven, eventually playing 53 official matches for Jong PSV. Sassuolo finished 11th in Serie A last season, having been promoted from Serie B the year before. Leysen will begin his Serie A journey with Sassuolo, who start their new season against Atalanta on Sunday.