The film follows Django, a slave played by Jamie Foxx who is freed by dentist-turned-bounty hunter Dr. King Schultz, played by Christoph Waltz.  The bounty-hunting duty eventually set out to free Django's wife Broomhilda, portrayed by Kerry Washington, from the clutches of the nefarious plantation owner Calvin Candie.  Leonardo DiCaprio is making Candie his first villainous performance.

Between Russell and Baron Cohen, the former had the more substantial role.  Russell was set to play Ace Woody, the violent and merciless trainer of Candie's male slaves forced into gladiatorial entertainment.  Via his @TheInSneider Twitter, Variety's Jeff Sneider broke the news of Russell's departure yesterday, tweeting, " First KEVIN COSTNER, and now KURT RUSSELL has EXITED the cast of QT's DJANGO UNCHAINED. No reason given or replacement named..."

As Sneider points out, Kevin Costner was originally tapped to play against type as Woody, but bowed out citing scheduling issues.  Russell, who worked with Tarantino on his Grindhouse contribution Death Proof, stepped in to play the miserable son of a bitch. 

Ain't It Cool has some more information regarding Russell and Django Unchained.  There's still no reason cited for his exit, but it was apparently amicable, with no hard feelings between the actor and Tarantino.  As for who will replace him the role, Tarantino did a quick rewrite and essentially folded Ace into the character of Billy Crash, meaning an expanded role for the always-fantastic Walton Goggins.

Moving on to Sacha Baron Cohen, who was set to play Scotty Harmony, a weak-willed Southerner who temporarily has ownership of Broomhilda before Candie strong-arms him out of the picture.  It's a small role pretty early in the picture, but the star of Borat, Bruno, and the upcoming The Dictator won't be making an appearance no matter how brief.

In an interview with Howard Stern, as reported by HitFix, Baron Cohen revealed, "That was going to be a cameo, but I had to drop out because of ['The Dictator''s] press tour."  Scheduling issues strike again.  Since Tarantino is heading towards that release date, casting wishlists have to take a hit in order to make the date.

So we won't be seeing Kurt Russell, Sacha Baron Cohen, or Joseph Gordon-Levitt (who was previously involved) in the supporting cast of Django Unchained, but the ensemble stills includes Garret Dillahunt, Samuel L. Jackson, James Remar, Don Johnson, Tom Wopat, M.C. Gainey, and Tom Savini.