Matsen shone on loan in the Bundesliga following his January switch, scoring two goals and providing two assists as Dortmund reached the UEFA Champions League final.
Despite eventually losing the Wembley showdown to Real Madrid, Matsen earned widespread praise for his spell under former Dortmund boss Edin Terzic, starting 22 of 23 appearances in all competitions.
The defender also impressed on loan at title-winning Burnley the previous season, being named in the Championship’s team of the season for 2022/23.
His contract at the London club was extended until the summer of 2026 in January, five months after the youngster rejected a takeover bid from Burnley.
After making 17 appearances for the Netherlands under-21 side, Matsen was initially left out of Ronald Koeman’s provisional Euro 2024 squad.
Born in Vlaardingen, Netherlands, Matsen began his career at the academies of Feyenoord, Sparta Rotterdam before being signed by Chelsea from PSV in 2018.