Zack Snyder reveals why Grant Gustin isn't "The Flash" in upcoming movie

The decision to not cast Grant Gustin who plays the character in the popular CW series of same name sparked controversy.

In a 2015 interview, Stephen Amell who plays “Arrow” in the CW series of same name, stated that Gustin should have been chosen for the role.

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Speaking to New York Daily News, the “Batman v Superman: Dawn of Justice” director explained why the star of The CW series was never in the running to reprise his role on the big screen as the speedster superhero.

“I just don’t think it was a good fit,” he said. “I’m very strict with this universe, and I just don’t see a version where … that (tone is) not our world. Even if Grant Gustin is my favorite guy in the world and he’s very good, we made a commitment to the multi-verse (idea), so it’s just not a thing that’s possible.”

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Recently, Gustin admitted that he would have loved to play the Flash in films, but supports the decision to cast Miller. “I’ve never met the guy, but I think he is a fantastic and interesting actor,” the actor said in January.

In the upcoming "Justice League," Superman (Henry Cavill), Batman (Ben Affleck), Wonder Woman (Gal Gadot), the Flash (Ezra Miller), Aquaman (Jason Momoa) and Cyborg (Ray Fisher) will unite to battle evil.

Ezra Miller’s movies include “The Perks of being a Wallflower,” “Trainwreck,” “Fantastic Beasts and Where to Find Them” among others.

Which of the two would make a better “Flash” in “The Justice League?”

Watch Gustin as The Flash in CW series below.