Cumberbatch will likely step into the role of Billy Bulger, brother to the famous mob boss. A reason was not given for Pearce's departure from the film. Depp (" Sweeney Todd," "Pirates of the Caribbean") stars as Whitey Bulger.
The film is based on the book "Black Mass: Whitey Bulger, the FBI, and a Devil's Deal." It is expected to arrive in theatres in 2015.
An Olivier Award winner, Cumberbatch's stage credits include the National Theatre's 2011 production of Frankenstein and 50 Years on Stage. He will star in Hamlet at the Barbican Theatre in August 2015.
Cumberbatch stars in the TV show "Sherlock," and his film credits include "August: Osage County," "The Fifth Estate" and "12 Years a Slave."