In another century, you could easily discern the difference between frontline and rear-echelon Mets. The starters were the starters and the bench guys were held in reserve until needed. When one of the bench guys got in the lineup, it usually meant a regular was aching or slumping or simply needed a blow. It was probably a Sunday, maybe the second game of a doubleheader, if you saw more than one of them in the same lineup. Or maybe you didn’t see any of them until the seventh inning on a Sunday (in the mind’s eye, these fellas only got into games on Sundays, perhaps indicating the starters stayed out too late taking advantage of their exalted status on Saturday nights).

If things were going reasonably well, your hardy band of backups would rally around their circumstances and adopt a collective nickname. One of the more famous, perhaps thanks to its presence on a superstation, was The Bomb Squad, Atlanta’s mid-’80s corps of veteran reserves who had the good sense to deploy the initials TBS. They played the bit to the hilt, posing in bomber jackets, goggles and other evocative surplus military gear.

The Bomb Squad wasn’t the first such group, however. Preceding them by a few years, albeit not building much of a profile or lasting terribly long, were the Mets’ own Bambi’s Bandits, the seasoned pros George Bamberger could call on in a pinch — which is precisely when a manager calls on seasoned pros. “Seasoned pros” are traditionally those players who would prefer to play every day (who wouldn’t?) yet have accepted their roles in the interest of extending their careers and maybe improving the health of their team. Circa 1982, at least before things began to crumble beyond Frank Cashen’s immediate repair, Bambi’s Bandits were comprised of a crack crew loaded with seasoned pro archetypes.

The backup catcher who’d been here forever: Ron Hodges.

The surehanded caddy to a defensively disinterested lumbering slugger: Mike Jorgensen.

The cursed with versatility utilityman: Bob Bailor.

The grumbly fourth outfielder: Joel Youngblood.

The sweet-swinging pinch-hitter deluxe: Rusty Staub.

Actually, if memory serves, Staub kept a dignified distance from identifying with Bambi’s Bandits — he was never a scrub and he wasn’t about to begin to adopt the persona of a scrub — but if you were talking “in a pinch,” how could you not talk about Rusty?

Before long, injuries and inertia took a toll on Bamberger’s starting lineup and Bambi’s Bandits inevitably blended into the everyday patchwork that became the 1982 Mets. Hodges took over for John Stearns. Bailor was pressed into continual service all over the diamond. Grumbly Youngblood was famously traded to Montreal early enough one Wednesday afternoon so he could record hits in Chicago and Philadelphia on the same day. The Mets limped home with 97 losses. Come June 1983, Bambi himself resigned, giving way to interim manager Frank Howard. The name “Hondo’s Heroes” was floated in the paper after somebody came off the bench and did something well, but I don’t recall it ever catching on.

The golden age of Met benches is long past, largely because eight-armed bullpens and six-man rotations have made backup players a luxury and lately because of the personnel blur that has overtaken Terry Collins’s best-laid plans. 2015’s nominal starting third baseman hasn’t yet resumed “baseball activities,” which could mean anything from taking grounders to spitting seeds. The starting catcher of record is magnetically drawn to the 15-day DL. The starting second baseman is, à la Joan Rivers on The Tonight Show, permanent guest host at third. There’s a starting left fielder who seemed to have started down the path to taking a load off his left knee, though he’s still active even if he hasn’t exactly been vibrant. There are also a couple of starting middle infielders who seemed permanently in flux until very, very recently.

Never mind not being able to tell the players without a scorecard. How can you keep track of who’s on the bench if everybody on the bench always seems to be playing?

Monday night in San Francisco, labels appeared useless. It’s hard to say who’s a solid “starter” in a lineup in which your catcher never figured to rise above fourth on the organizational depth chart, your left fielder is a guy you literally couldn’t give away twice and your first baseman is your first baseman only because a) that knee business must be killing him and b) your actual first baseman hasn’t made anything but the most accidental/incidental of contact in at least a month.

When this game began, the catcher, Johnny Monell, was batting .182; the left fielder, Kirk Nieuwenhuis — recalled more out of desperation than any crying need for another look at Las Vegas’s favorite frequent flyer — was at .100 on his major league season, a scant .079 counting only his earlier Met tenure; and Michael Cuddyer, to whom millions upon millions were given last November, had sunk to .236. His body of work from June 20 through July 5 consisted of 36 at-bats and two base hits.

Cuddyer. Nieuwenhuis. Monell.

Diminished. Discarded. Dubious.

In Collins’s batting order, they were 5-6-7. And to make their inclusion in a major league lineup found anywhere outside a split squad game on a St. Lucie back field at 10:30 in the morning that much more absurd, they were asked to face the only pitcher in the past two decades to have no-hit their team.

Chris Heston wasn’t nearly as untouchable in San Francisco as he had been in New York last month. Ruben Tejada, who struck out to complete history on June 9, broke up Heston’s no-no with one out in the first. So much for drama. But it wasn’t like Chris was getting touched, either. The Giants were undeniably sloppy and most likely sleepy — much was made of their courageous decision to go back to their hotel in Washington Sunday night before flying home on Monday morning — but it didn’t damage them in the tops of innings at Phone Company Park. Heston walked four, fumbled a relay and threw away a pickoff, yet yielded only three singles in seven-and-a-third innings.

If getting a hit off Chris Heston was on the Mets’ bucket list, mission accomplished. But scoring a run eluded them through eight. Meanwhile, Heston’s mound opponent, Jon Niese, continued to reap the benefits of the six-man rotation, a dicey configuration set up to benefit basically everybody but Jon Niese. Niese has been close to brilliant on extra rest every time out. Pitching for the Mets, however, has prevented him from laying claim to any wins for two months.

Perhaps the Mets would like to consolidate their rotation by having Niese pitch for another team (in exchange for a useful bat attached to a useful swinger of said bat). He’s certainly making himself attractive in his weekly appearances. Monday night Jon went eight, scattered three hits, walked two and didn’t implode when presented the opportunity, which certainly offered a welcome twist to the usual storytelling. A brief bout of wildness loaded the bases in the sixth, which is the inning most Niesewatchers circle in anticipatory dread as the money inning. Bet on Niese finding a way to give up a run or more in the sixth and collect big. Even the New York Lottery advertises, “If Niese is in it, the other team will win it!” Except this time — with the bestest Buster since Keaton standing approximately 60½ feet away — Niese persevered in the other direction. He found a way to retire Buster Posey and kept the game tied at zero.

Keeping a game knotted at zero is generally the best a Mets starting pitcher can hope for. Save for the occasional oddball offensive outburst that surrounds (and is instigated by) Steven Matz, we know the Mets don’t hit for any of their starting pitchers. We know their starting players are relentlessly disappointing and that their bench has faded faster than Marty McFly’s family picture. There are never more than four players attached to it and there is rarely an air of dependability to their presence. There is mostly the Las Vegas 51s Alumni Club having its nightly meeting, save for those nights when one or more of them is starting because it’s not like the starters are getting anything going.

The top of the ninth arrived scoreless and the cynical assumed it would stay that way. Due up were first baseman Cuddyer — in there because Lucas Duda is rapidly devolving into what certain Civil War historians would call a lost cause; left fielder Nieuwenhuis — in there because relative phenom Ceciliani lost his shine from incessant exposure to big league pitching; and catcher Monell, whose ability to leapfrog Anthony Recker may have been his greatest athletic feat to date in a Mets uniform before last night.

Oh, but last night…last night the Mets we deride most were the Mets from whom we derived the most pleasure, the most exhilaration, the most — dare we say it? — hope.

Cuddyer singled sharply to left off Sergio Romo, the same Sergio Romo who managed to give up a game-ending single to the same Michael Cuddyer 25 days (and 9 Cuddyer base hits) ago.

Nieuwenhuis, somehow back after his designation for oblivion, failed to bunt Cuddyer to second, which was great, actually, because it left him no viable option other than to double to right. Cuddyer, barking knee and all, put on the speed of a man half his age (which isn’t really 103, despite all that snow on his well-compensated roof), and threatened to score. It was an idle threat. Michael stopped at third. Kirk refamiliarized himself with second. Two in scoring position, nobody out.

Monell would face Santiago Casilla, which begged the question of 1982 Mets backup catcher from after Stearns got hurt (which means he wasn’t good enough to play in front of perpetual scrubeenie Hodges) Bruce Bochy, “You’re actually bringing in a pitcher specifically to face Johnny Monell?”

Johnny Monell, the .182 wonder?

Johnny Monell, who got to .182 from .095 the week before by getting on what for him qualified as a torrid streak yet .200 was a distant dream?

Johnny Monell, who the legendarily wise, lavishly bejeweled Bochy saw no need to keep around despite an eight-game front row seat to his talents in 2013?

Yes, indeed. One of the greatest managers of the modern era brought in a pitcher specifically to face Johnny Monell. Or simply decided he’d seen enough of Romo, the man who gave up two ninth-inning hits in the same season to Michael Cuddyer. Or was so tired from that Sunday Night Baseball ordeal that he nodded off and inadvertently unhinged the receiver to the bullpen phone.

Whatever. It was Johnny on the spot I don’t think anybody would have forecast when he and Nieuwenhuis were tearing up Spring Training (note to self: disregard everything about Spring Training). It was the ninth inning, the score was nonexistent, the game was on the line, the Mets were facing the defending world champs and the batter was Johnny Monell.

The batter who drove in the go-ahead run and the insurance run — and would next carry on his very own back an additional run besides — was also Johnny Monell. Coincidence? I looked it up, and nope. It’s the same guy. It’s the same Johnny Monell who lashed a double to drive home Cuddyer and Nieuwenhuis to make it Mets 2 Giants 0. The part where Cuddyer and Nieuwenhuis score, let alone the part where the Mets take a late lead, reads as strange. But Cuddyer was once good and Nieuwenhuis we can vaguely recall doing something a couple of seasons ago. But Johnny Monell? Johnny Monell gets the big extra-base hit? Then comes around when Juan Lagares suddenly singles? And probably thinks to himself, “So, this is what home plate looks like from the vantage point of the baserunner — who knew?”

Yup. That’s the Johnny Monell who swiped a lead in San Francisco, not to mention caught Niese’s eight shutout innings, along with oughta-be All-Star Jeurys Familia’s perfect ninth. Those are the Mets, who have no bench, but somehow found enough in reserve to defeat the Giants after taking two of three from the Dodgers. Those are the Mets — DFA-laden, Quadruple-A-speckled, too often classified 4-F — who have outscored their opposition 14-0 over the last 20 innings.

These are our Mets, and just when you’re ready to write them off, you best check the waiver wire, because sometimes the guys you least suspect will be designated for excitement.