We were prepped for Robert Duvall’s Big Moment for a decade before it happened.

From “The Godfather” (1972) through “Network” (1976), “The Great Santini” (1979), “Apocalypse Now” (1979) and “True Confessions” (1981), people who knew acting and film scholars with an eye for the long game were in lockstep.

“WATCH” this guy, they all said. This is how it’s done.

Then “Tender Mercies,” the validation of an Academy Award, and everything that came to DeNiro in a blinding blur — the acclaim, the Oscars and Oscar nominations, “legend” status — finally came to Robert Duvall just as he entered his 50s.

Glory and the decades of acclaim-as-his-due that followed arrived on the back of a small, intimate film from the Aussie director of “Breaker Morant” and the playwright and screenwriting legend who adapted “To Kill a Mockingbird” and wrote all versions of “The Trip to Bountiful” — play and screenplay.

The memory has been conditioned to recall only what became the signature scene of this film, the clip that ran when Siskel & Ebert praised it on their view show, wherever Duvall showed up on TV to promote it and which remains its iconic moment to this day.

He plays Mac Sledge, a country music has-been, a Willie Nelson singer/songwriter type who let the bottle and heartbreak get the better of him, but who sobers up for a good woman (Tess Harper), a widow, and her little boy. Duvall as Sledge gets across the gift, art and craft of songwriting as he strums out the bones of a tune to the kid, Sonny (Allan Hubbard) as Mom watches on, a homey scene set in a rural Texas kitchen with just actors, a simple melody and heart.

Two-time Oscar winner Horton Foote’s screenplay has a few grace notes like that, and some hard-won Texas working class country music suffering simmering beneath the surface as Sledge begins his unlikely path to redemption. He gets left behind by a friend, post-bender, at the tiny Texas filling station/store and motor hotel run by Rosa Lee (Harper), widowed by the Vietnam War some ten years before.

Foote, who also had a Pulitzer Prize attached to his reverent obituaries back in 2009, gets at the heart of Texas, rural folks of a certain generation, and at the despairing working class soul of country music with this simple redemption story.

Mac finds himself singing in church, watching over Sonny as Rosa Lee sings in the choir, trusted to run errands and expected to do the right thing — stop drinking — without her having to ask.

That he does, with no judgement coming from her, is as country music as it gets, “Good hearted woman lovin’ a good timin’ man” and all.

Betty Buckley plays the bitter country star ex that Mac finds himself trying to reconnect with, if only to get her manager (the great Wilford Brimley) to show his new songs around Nashville.

Mac isn’t looking for notoriety, a “comeback.” Otherwise he wouldn’t blow off the reporter (Paul Gleason of “The Breakfast Club”) twisting his arm for a “star now pumping gas” story. Whatever he’s doing — sobering up, walking the line, trying to make some real cash — is for “her” and “the boy.”

Ellen Barkin was just a babe in the biz playing the sad, needy daughter Mac never got to know. Buckley brings her Broadway voice to a country chanteuse who has started to feel the miles.

And Harper, making her big screen splash in this 1983 classic, dazzles by doing as little as possible — an understated performance of dignity, pragmatism and love that isn’t gushed or even admitted out loud.

The film’s quiet authenticity made it something of a watershed, and most everybody in it went on to do great work — Foote turning his play “The Trip to Bountiful” into an Oscar winning movie, Beresford helming “Driving Miss Daisy,” Harper enjoying a long, widely-admired career than included “No Country for Old Men,” “Crimes of the Heart” and indie films and more episodic TV than a body can recall.

Duvall? He took his new status and made indie films with Oscar potential (“The Apostle”), showy turns in the odd blockbuster, and work that ensured Billy Bob Thorton’s “Sling Blade” was Oscar worthy, that Jeff Bridges (“Crazy Heart”) got an Oscar, too, and that Bill Murray (“Get Low”) at least had a shot at one.

“Tender Mercies” became something of a landmark in all their careers, and you can see Duvall’s considered introspection in every film he’s done since, from TV’s “Lonesome Dove” to “Open Range,” to films he’s directed himself — “Wild Horses,” “Assassination Tango” and “The Apostle” among them.

But the best thing about this classic is you can watch it now and wonder, even all these years later, what took Hollywood so long to realize that the best among them was the one player who never called attention to himself. He let you find him, and feel all the richer for it.

Rating: PG

Cast: Robert Duvall, Tess Harper, Ellen Barkin, Wilford Brimley, Allan Hubbard, Paul Gleason and Betty Buckley

Credits: Directed by Bruce Beresford, scripted by Horton Foote. A Universal (EMI) release on Youtube, PosiTV, etc.

Running time: 1:32