Morey was injured during the broad victory over Holstein Kiel in the semi-finals of the German Cup by 5-0.
Morey fell wrongly, causing a severe injury to the right knee, causing teammate Erling Haaland to place his hands over his head from the horror of the scene while sitting in the stands.
Morey is set to undergo knee surgery that will keep him out for a long time, which would put him out of the calculations of Luis de la Fuente, Spain’s coach in the Olympics, several weeks later.
Dortmund captain Marco Reus said after the match: “Matteo was seriously injured, and this covers the victory we achieved.”
He added: “Anyone who sees the scene will think it is a severe injury, we hope it is not, but it looked very strong.”
Morey, 21, is a promising right-back for Spanish football, who played in Barcelonas La Masia academy, before moving to Dortmund in 2019.
Morey has played 24 matches for Dortmund this season, taking advantage of Achraf Hakimi’s departure to Inter Milan.
Spain is in the same group with Egypt, Argentina and Australia in the soccer tournament in the Tokyo Games.