Michael Kelly is not too proud to admit that, while Clint Eastwood may have made his day, he also ruined one of his nights.

“I think I slept two hours the night before,” says the actor of his first day at work on the Oscar-winning director’s latest film, “Changeling.”

“My wife was rubbing my shoulders the entire time. I was a wreck. I kept thinking, ‘They’re going to recast me.’ ”

Kelly needn’t have worried. His nuanced performance as Det. Lester Ybarra — the cop who risks his job and goes up against the LAPD’s rampant corruption in order to solve the Wineville Chicken Murders and validate Christine Collins’ (Angelina Jolie) claim that the child returned to her is not her own — grounds the fact-based period film.

It was a dream gig for the New York-based character actor, who previously had a recurring role as one of the feds investigating Tony on “The Sopranos” and first got noticed with the 2004 pic “Dawn of the Dead.”

“You spend your whole life wanting to be Clint Eastwood, and at a certain point you realize you’re never gonna be that cool,” Kelly says. “But getting to work with him is almost as cool.”

Kelly almost didn’t get the chance. When he learned that Eastwood had liked his taped audition, he was in the midst of a six-month shoot in Africa for the HBO miniseries “Generation Kill.”

“HBO could’ve been like, ‘Dude, we own you,’ ” he says. Instead, the cabler worked with “Changeling” producers in order to accommodate his participation in both. For Kelly, that meant more than one 16-hour trip between Mozambique and Los Angeles, where “Changeling” was shot late last year.

“Thank goodness ‘Generation Kill’ was a military thing, so the hair, or what I have left of it, worked out for both,” he says with a laugh.

He admits that Eastwood’s infamous one- or two-take style — which for Kelly included a lengthy Steadicam shot that took him from the car to the chicken coop to a chase on foot into a nearby house — spoiled him for other projects.

“After that, typical 10- to 12-hour days seem really, really long,” says the actor, who next co-stars alongside Russell Crowe in “Tenderness.”

The actor stresses he’s hardly complaining about extended shoots on the set. Fact is, he might be getting a lot more work after “Changeling” opens, but he’s not raising his own expectation.

“I’ve been through it before, where you think maybe a certain role is going to take you to the next level or whatever you want to call it,” he says. “Still, it’s hard not to hope that this one does.”

An actor should always:
“Be thankful when working.”
Lucky break: “That’s a no-brainer: ‘Changeling.’ “
Favorite film character: Paul Newman in “Cool Hand Luke.”