In person, "he's so charming, he's so funny," Chastain says. "It's like yes, I believe the entire world would come together to rescue Matt Damon."
A solo performance is a notch on the belt for the star, who first wowed Scott with his sly, deft performance in 1999's The Talented Mr. Ripley. Chastain calls Damon a character actor hidden in a movie star's body. "He always plays these really interesting characters," she says. "You look at his career and you look at The Informant and you look at Behind the Candelabra. … He really is one of the best we have."
Here on Earth, Damon, his wife and four children are settled in to life in Los Angeles, having moved from New York two years ago. A proud smile crosses his face when he talks about his kids. "My oldest daughter just got her license yesterday," he says. He taught her how to drive. "She would drive last year just to school every morning. We'd get in the car and drive."
But we never see pictures of Damon's brood – ever. Damon famously avoids A-list watering holes, and he manages to keep a low profile, even in paparazzi-laden Hollywood. "He's very happy having a private life, which I really respect," Chastain says.
Even still, "it's different at 44," he admits. "I've been on a strict diet and training like crazy. So I'm in better shape than I ever was for the other ones. Also Paul was really specific about wanting the character: If the movie opens and the first frame of me looks like a guy has been living too well" -- he grins -- "the movie's over."