Yup. Pretty much what the title says.
Matt Damon was originally signed on to star opposite Mark Wahlberg in The Fighter, but due to scheduling conflicts, Damon dropped out of the project. Brad Pitt is poised to take Damon's place in the film.
Refresh my memory...
As Variety puts it:
Pitt is in negotiations to play Dicky Eklund, Mickey’s half-brother and a talented fighter who once went the distance with Sugar Ray Leonard in a title fight but then turned to crime and landed in prison. He turned his life around and helped his underperforming brother find the spark for a remarkable run that led to the world title.
So... they're replacing one handsome boxer with another?
Yes! It would be very cool if all three of these actors could be in this movie, but alas, there's only room for two. Still, if Damon has to be replaced with anyone, I'm completely okay with it being Brad Pitt.