In July, it was confirmed that Keaton had signed on to appear in the upcoming film, a remake of Bille August's 2014 Danish movie "Silent Heart".
However, editors at Deadline have now reported that Keaton will no longer appear in the film, with Sarandon replacing her in the part of a terminally ill mother named Lily who arranges to bring her family together one last time before she dies.
Danish writer Christian Torpe, who penned the screenplay for "Silent Heart", has also written the new adaptation. Production on the film is due to kick off this month in the United Kingdom.
Keaton has not commented on her decision to drop out of the film. The Oscar-winning actress was most recently seen onscreen in romcom "Book Club" alongside Jane Fonda, Mary Steenburgen, and Candice Bergen, and is currently in the post-production phase on "Poms", Zara Hayes' comedy about a group of women who form a cheerleading squad at their retirement community.
The 72-year-old has a string of other projects in the mix too, including a role as Dr. Sylvia Mansfield in short thriller "Slipping Away" and as Thelma Toole in "Butterfly in the Typewriter", David DuBos' forthcoming movie about troubled author John Kennedy Toole and his struggle to bring his comic masterpiece "A Confederacy of Dunces" to print, with the project also starring Diane Kruger and Nick Offerman.
A potential release date for "Blackbird" has not yet been set.