Sienna Miller has been cut from 'Black Mass'.

The 33-year-old actress filmed scenes as Catherine Greig, the girlfriend of Johnny Depp's character Whitey Bulger, for the upcoming biopic on the infamous Irish-American mobster Bulger but they were left on the cutting room floor.

Director Scott Cooper told the Boston Globe that although Sienna was ''fantastic, it came down to narrative choices''.

He explained that a decision was made to focus on Bulger's life before he left Boston, rather than during his years as a fugitive when Catherine was his girlfriend.

Last year Sienna admitted to doubts about her Boston accent, revealing that she had worked hard with a dialect coach before filming.

She said: ''Up until the day before I flew here, I couldn't do it and it sounded stupid. 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.''

Other actors who star in the movie include Benedict Cumberbatch, Dakota Johnson, Joel Edgerton, Juno Temple, Corey Stoll, Kevin Bacon, Adam Scott and Peter Sarsgaard.