According to a report from Page Six, Hamm was up for the starring role in the film adaptation of Gillian Flynn's Gone Girl, but was contractually obligated to his role as Don Draper in Mad Men, which creator Matt Weiner allegedly wouldn't let him out of to play the suspected murderer.
"Matt would not let Jon out of his contract to do Gone Girl. Jon was really upset about it at the time—and is still upset, because he's thinking about the future of his career as Mad Men comes to a close," a source dished to the New York Post column.
Another source revealed that Hamm couldn't participate in Gone Girl because of his conflicting shooting schedule for Mad Men. But now that his long-running series is coming to an end, the Million Dollar Arm actor told GQ he honestly has no idea what's next for him, despite his co-stars already locking down other jobs.
"Look, the one constant thing I've had in my career is now removed. And that's an eye-opener: Are people still going to take me seriously? Am I just going to do romantic comedies for the rest of my life? What's next? And I don't know, you know? I wish I was smug enough to have had a grand plan," he told the magazine.
"I guess some people would say, 'Okay, the last three years of Mad Men is going to be like this: I want to do a play. I want to do this. I want to do that.' I was just like, 'I want to do something that seems cool," he added.
His longtime girlfriend, actress Jennifer Westfeldt, also revealed that playing the successful ad man took its toll on her boyfriend, but ultimately saw a sense of relief in him once the show wrapped. "It's a confusing juxtaposition. I think the darkness of Don has weighed heavily on Jon, despite it being the role of a lifetime and the opportunity that gave him the career of his dreams," she told GQ.
"The end was of course bittersweet and complicated for Jonny."
But leaving Don Draper behind might have proved more difficult than either one could have imagined. NBC News confirmed last week that Hamm completed a month-long stint in rehab for alcoholism.
"With the support of his longtime partner Jennifer Westfeldt, Jon Hamm recently completed treatment for his struggle with alcohol addiction," a rep for the actor said in a statement. "They have asked for privacy and sensitivity going forward."
E! News has reached out to AMC for comment.