That’s right: Emily Blunt was originally slated to playBlack Widowin the Marvel Cinematic Universe (MCU).
Would Emily Blunt want to return to the MCU?
However, she didn’t have a choice.

Blunt opened up to Howard Stern about losing the role.
“For me, it’s all about the part,” she told Stern.
We have no doubt she will appear in a MCU film or series in some capacity in the future.