The Hollywood heavyweight became good friends with The Office actor after co-starring with his wife Emily Blunt in The Adjustment Bureau.
Krasinski had been working on a new drama about a salesman in a small town, and Damon soon hooked up with his pal on the project.
He tells Parade magazine, “It’s been really fun writing with John. It reminds me of writing with Ben (Affleck). What worked about writing as partners was that it’s like ping pong. Nobody arrives with a complete idea.
“You arrive with the germ of an idea, and that gives the other guy an idea, which gives you an idea, which gives the other guy an idea. So where it gets really exciting is when these ideas come up between the two of you and you can’t even figure out what the genesis was. What it requires is a partner who has similar taste and a similar sense of humour.
“(We) started writing on weekends, while I was doing We Bought a Zoo. I went into it without any real expectations. I liked spending time with John. But it took on a life of its own and got really exciting.”