First off: There’s really no such a thing as a casual Replacements fan. People either don’t get what the big deal is or worship the Minneapolis rock forefathers, with that particular brand of emotional reverence reserved for music that has some kind of rarity, a precariousness to it. In the case of the ‘Mats, this is at least partially born of their breakup in 1991 — the swingin’ party that ended much too soon, with terrific, booze-soaked theatrics, leaving behind a question mark about what could have been had its attendees not seemed hell-bent on mutually assured destruction.

At the Masonic last night, some 3,300 fans — nary a casual one amongst them — got the chance to answer that question for themselves, thanks to the Replacements’ 2013 reunion and San Franciscans’ year and a half of patiently waiting until the guys got around to visiting our fair city. Yes, from the looks of the room, last night was a night to forget it was Monday, hire a babysitter, throw on that faded black punk band t-shirt from the back of your closet, and jump up and down with both arms extended in a kind of religious fervor, screaming the words to “Bastards of Young” back at one surprisingly sprightly and good-natured Paul Westerberg, gray hair (his and yours) be damned. It was, after all, the band’s first Bay Area gig in over two decades, and the scent of once-in-a-lifetime, pinch-me-this-can’t-be-real wish fulfillment hung in the air alongside the beer and the sweat and the weed.

“We used to play in the lowlands,” said Tommy Stinson to the sold-out crowd at one point, recalling the band’s last gigs in San Francisco. “Now we’re at the top of the hill. Anyone remember the I-Beam?,” referring to the small Haight Street underground rock nightclub of the ’80s and early ’90s. “Remember the I-Beam?!”

“I barely do,” said Westerberg. A few minutes later, on playing the city’s “mountain top”: “I think I pulled a hamstring.”

Signature self-deprecation and “ha, we’re old” references aside, this was about as far from a typical reunion show as one could hope for from a bunch of middle-aged dudes finally capitalizing on a legacy that has only grown more weighty in their absence. This is a good thing. They churned through the hits, of course, to the degree that the Replacements can be considered to have had hits — “Can’t Hardly Wait,” “I Will Dare,” “Left of the Dial,” “Alex Chilton” — but they also know their fan base at this point, and their fan base wants the deeper cuts too. They want “Hangin’ Downtown,” they want “The Ledge,” they want “Sixteen Blue,” “If Only You Were Lonely,” “I’ll Be You,” “Androgynous,” “All Shook Down,” “Seen Your Video” and “Within Your Reach.” They want Westerberg solo, fingerpicking a guitar, singing “Skyway” like he’s trying to lull you to sleep and break your heart at the same time.

We got all this and more last night. We got loud. We got a punk band, in case anyone had forgotten from which swampy underground the Replacements first emerged in 1979. And we got a glimpse of what it looks like when musicians who were once known as much for their tendency to fall down onstage as for their technical skill are actually in command of their considerable catalog. Westerberg shone on guitar solos; Stinson expertly grounded him on bass when necessary. They played covers, or parts of covers, including two T. Rex tunes — “20th Century Boy” and “Bang a Gong” — Elvis Presley’s “Little Sister,” Black Sabbath’s “Iron Man,” Millie Small’s “My Boy Lollipop,” Dave Brubeck’s “Take Five,” and a jovial, dance-party rendition of Chuck Berry’s “Maybellene.” They were loose, relaxed, but in the way an exceedingly good bar band should be. A few skipped lyrics here and there, a few antics (Westerberg singing parts from inside a red camping tent that remained onstage for the duration of the two-hour set?), but for the most part this was a band with very little to prove, and in consummate control.

That’s not something you see every day. There’s an inherent rust and jaggedness to the Replacements’ edge, along with a laid-flat vulnerability, that instills in the listener that immediate ring of authenticity — a sense that we’re in good hands here, people, we can trust these guys — that rarely comes across from the crop of younger rock ‘n’ roll bands who have sprung up in their place, even the ones who name-check the ‘Mats with abandon. (We would have bet money that Green Day’s Billie Joe Armstrong, a member of the pack of proud ’90s alt-rock purveyors who point to Westerberg as a songwriting godfather, and who played with the Replacements at Coachella last year, was going to join the guys onstage at some point. Alas.)

Even at their most sober and most radio-friendly, Replacements songs hit in the chest because they’re honest, and sad, and sometimes filthy, or maybe honestly sad and filthy; there’s just nothing studied, no posturing about ’em. To be fair, when you have a hard time remaining upright for the duration of a set, as the Replacements did for much of their time together, it’s pretty easy to avoid striking a pose. Still: The power of raw sincerity is not to be underestimated.

To take in that roughness, that earnestness, that sore-throated desperation, in a squeaky-clean new(ish) Nob Hill venue like the Masonic was, certainly, a little comical, especially with that venue’s army of ushers and near-totalitarian rules about comings and goings from the general admission floor area. One can only imagine the final tally of flipped birds, screamed epithets and broken beer bottles had the late ’80s version of the Replacements somehow found themselves playing such a room. As it were, the gents were on something like their best behavior, to the point that Westerberg lighting a cigarette for the encore nearly sent a ripple through the crowd.

All things considered — and let’s be honest, if the Replacements had continued to be the late ’80s version of the Replacements for even another half-decade, it’s unlikely that Westerberg would even be alive — we’ll take it. It was hard not to feel, as Westerberg launched into “Left of the Dial,” perhaps the prettiest pop song ever penned about musical obscurity, and two-thirds of the crowd roared along with him “Read about your band, in some local page…” that the Replacements represent the most triumphant possible outcome for any band that began as the Replacements did. Martyrdom at the altar of ’80s punk might be the flashier option, but in this version we get to have that giddy chill of recognition at the first note of the guitar solo on “Alex Chilton,” and watch as formerly too-cool strangers all around us break into knowing, shared grins, freaking out together in syncopation. Pinch-me-this-can’t-be-real stuff, if you’re willing to take a non-casual fan’s word for it. Here’s hoping we don’t have to wait another 16 years to do it again.

Note: Opener John Doe is yet another member of the “has serious punk cred but also seems like he’d just be great to go fishing with” club. Sprinkled throughout his solo, folkier work were three X songs: “Burning House of Love,” “The New World,” and “The Have Nots” — on which he changed the name of one of the bars in the song’s lyrics to “The Make Out Room.” Nice local touch.