Can Eldritch Strike impose disadvantage on a saving throw for a spell you had previously cast?

Can Eldritch Strike impose disadvantage on a saving throw for a spell you had previously cast?

— Armando Doval (@armando_doval) May 23, 2018

Eldritch Strike imposes disadvantage on the next saving throw the target makes against a spell you cast. This benefit expires at the end of your next turn, and it works against a spell you cast at any point. The key is that the save is made before the end of your next turn. #DnD https://t.co/JJVjjFs1wm

— Jeremy Crawford (@JeremyECrawford) May 23, 2018