Tuesday night’s twofer pairing of Willie Nelson and Kris Kristofferson at Vetter Stone Amphitheater in Mankato had two sunsets for a backdrop: the literal one that glowed over the Minnesota River alongside the picturesque outdoor venue, and the figurative sunset that has been lingering over the long-sold-out concert since April, when fellow American music icon Merle Haggard died.

Haggard’s passing served as a reminder to catch these once-unstoppable country music giants while they’re still going, a sentiment that especially hit home during Kristofferson’s opening set.

The legendary songwriter and storied 80-year-old actor — who performed with Haggard just this past September at the Minnesota State Fair — showed signs of the fading memory and worsening physical state documented in a Rolling Stone profile last month. However, he toughed it out in a way that seemed so Kris Kristofferson, earning several standing ovations from the 3,000 or so attendees. He also filled in the gaps and raised spirits even higher by bringing along Haggard’s stellar band, the Strangers, to perform with him.

With Merle’s sons Ben and Noel Haggard leading the way, the Strangers breezed through a half-dozen of The Hag’s classic songs while Kristofferson caught his breath at various intervals. “Running Kind” and “Rambling Fever” rang out like anthems for the show’s resilient stars, the latter song spiked with potent guitar picking by young Ben Haggard that suggested he, too, could become a star. “Okee From Muskogee” then prompted a big singalong at show’s end. The crowd also dutifully filled in for Kristofferson’s faded voice on “Me and Bobby McGee” and “Sunday Morning Coming Down.”

Nelson, 83, and his Family band also sounded a little ragged at first as they kicked off their set with the requisite “Whiskey River.” By the time ol’ Willie plucked out his first wizardly guitar solo in “Still Is Still Moving” one song later, though, it was clear there would be much more than just sentimental value attached to the concert’s $43-$143 ticket prices.

Few American masters remain as masterful at this point of their careers as Willie is, a point highlighted Tuesday as he picked his way through more landmark songs that reminded us of our other lost giants: Ray Charles in “Georgia on My Mind,” B.B. King in “Night Life,” Waylon Jennings in “Good Hearted Woman,” Elvis Presley in “Always on My Mind.” Nelson delivered them all with effortless verve, his voice holding up strong and his guitar playing cutting through each song with surgical precision.

With his older sister Bobbie Nelson also sounding sharp on piano and longtime drummer Paul English behind him lighting up the stage with smiles, Willie threw a couple of pleasant surprises into his 75-minute set, including his recent Haggard collaboration “It’s All Going to Pot” (ahem) and the farmland-rooted “Promiseland.” Not surprisingly, though, the crowning moment came during the evergreen “Angel Flying Too Close to the Ground,” with words Nelson has sung thousands of times, but never with so much meaning attached: “So leave me if you need to / I will still remember.”

Simply put, Tuesday’s show was unforgettable.