Poor Jeremy Renner!
To be told you're too old (read: look too old, obviously) at 36 to play a 34 year-old, only to be replaced by someone close to a decade older than you!
(From the trivia section:
"Jeremy Renner was originally considered for the role of Robert Ford, but he was ultimately thought to be too old for the character.")
OK, so Brad Pitt's company produced the film, so obviously he had the power to insert himself into what he saw as a plum role, so all that's all pretty moot. Or, probably more likely, the role came first, then the producing aspect.
(Although Brad's showing his age these days, I would say he did just about look acceptable as man in his mid-thirties, especially as they had harder lives back then, and no metrosexual moisturising routines to speak of.)
Still, poor Jeremy, eh?