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
I’m honestly flabbergasted.
The text reads as follows: “When you hit a creature with a weapon attack, that creature has disadvantage on the next saving throw it makes against a spell you cast before the end of your next turn.”
In standard English grammar, that means the creature has disadvantage against spells that are cast AFTER you hit the creature, but BEFORE the end of your next turn.
To achieve the meaning Mr. Crawford suggests, it would need to be worded as: “…that creature has disadvantage on the next saving throw it makes against a spell you cast UNTIL the end of your next turn.”