Sienna Miller’s scenes in the upcoming Johnny Depp movie, "Black Mass," have been suddenly given the chop.

The 33-year-old actress was slated to play Catherine Greig, a girlfriend of real life gangster Whitey Bulger (played by Depp) in the crime thriller, but producers decided to go in a different direction at the last minute.

Director Scott Cooper told The Boston Globe although Miller was “fantastic” alongside Depp and the slew of big names who appear in the film, it “came down to narrative choices.” "Black Mass" is due to hit cinemas September 18.

Click here to subscribe to FOX411’s YouTube channel

Miller opened up last year about the lengths she went to in preparation for the role, revealing that she even worked with a dialect coach to make her Boston accent believable.

“Up until the day before I flew here, I couldn’t do it and it sounded stupid,” she said. “And I was sort of religiously watching every film ever set in South Boston: 'Good Will Hunting,' 'Gone Baby Gone,' 'The Town.' Catherine had a thick accent, so I hope I do it justice.”

Depp is unrecognizable as Whitey Bulger, the Boston mobster who was sentenced to life in prison after a 16-year manhunt, found guilty of 11 murders.

"Black Mass" also stars Benedict Cumberbatch, Kevin Bacon, Joel Edgerton, Dakota Johnson, Adam Scott and Corey Stoll.

This article originally appeared on News.com.au.

Four4Four: Will contestant lose virginity on TV?