Bayer Leverkusen have officially completed a major deadline-day return as their extensive summer rebuild continues under Carles Martinez.
The Bundesliga club have undergone significant changes following the departures of several important first-team players during the window.
Alex Grimaldo joined Atletico Madrid, Piero Hincapie moved to Arsenal and Exequiel Palacios completed a transfer to Ipswich Town.
Leverkusen responded by strengthening several areas, with Miguel Gutierrez, Facundo Medina, Afonso Moreira and Kennet Eichhorn among their additions.
Their latest move brings a familiar attacking player back to the BayArena after three years away from the club.
Bayer Leverkusen have officially confirmed the permanent return of Moussa Diaby from Saudi Pro League side Al-Ittihad.
The French forward has signed a contract running until June 30, 2031 and will once again wear the number 19 shirt. The German club paid €30 million to secure his signature.
Diaby previously represented Leverkusen between 2019 and 2023 after arriving from Paris Saint-Germain.
During that first spell, he registered 49 goals and 48 assists across 173 competitive appearances for the German club.
His performances eventually earned him a club-record £51.9 million move to Aston Villa in July 2023.
Diaby appeared in all 38 Premier League matches during his only season at Villa, contributing six goals and eight assists.
He then joined Al-Ittihad, where he recorded four goals and nine assists from 31 league appearances during the 2025–26 campaign.
The winger also contributed one goal and five assists across nine AFC Champions League Elite matches.
Manchester United, AC Milan, Tottenham, Benfica and Inter Milan were all linked with Diaby during the summer window.
Sunderland also reached an agreement with Al-Ittihad, but that proposed transfer collapsed because of work permit complications.
Leverkusen ultimately secured his return instead, adding the former PSG academy graduate to a squad that has undergone major changes.
Diaby now begins a second spell at the BayArena as Leverkusen continue reshaping their attack for the 2026–27 season.
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