They were coming off a sublime campaign under rookie head coach Ben McAdoo, ordained an offensive guru who was fortified with sagacious free agent signings on defense. All three mercenaries — Olivier Vernon, Janoris Jenkins and Damon “Snacks” Harrison — played past the back of their glittering football cards. Then this year, the Giants signed all-world wideout Brandon Marshall, whom, with Odell Beckham Jr. in his prime and Sterling Shepard entering his, gave us the sense that the world was their Big Blue oyster.

Rather than provide the generic box-score breakdown and parse the statistical particulars, there’s one moment that flawlessly conveys the Giants’ struggles and their eyesore of a season. An otherwise ordinary play in the second half led to an extraordinary remark. And it was a complete, pristine microcosm of that team at this time.

If you’ve listened to Darryl “Moose” Johnston over the years, you’ve noticed two things about his public mien. He’s very good at breaking down football plays, and he’s also vehemently neutral. A hardworking, bruising fullback during his days in Dallas, Johnston is an equally blue-collar commentator — fair and firm.

It takes a lot to make Moose’s blood bubble. Yet such a play occurred Sunday during the Giants-49ers game. The Niners handed the ball to running back Carlos Hyde, who ran off tackle. Shortly after blowing past the line of scrimmage, Giants cornerback Janoris Jenkins was the first defender in front of him. Rather than blasting his chest, wrapping his waist or lunging at his legs, Jenkins went full matador, stepping toward the halfback before offering full, free passage.

Perhaps nothing shreds Johnston’s gridiron sensibilities more than an NFL player allergic to hitting. Moose called out Jenkins — with clear contempt in his voice — for totally avoiding contact. Jenkins isn’t some practice squad player or marginal talent who is 52nd on a 53-man roster. Jenkins is a stud, a perennial Pro Bowl talent, whom the Giants signed to five-year, $62 million contract with a $12.5 million annual salary, $10 million signing bonus and $28.8 million in guaranteed money. Jenkins makes $12.9 million this season. Jenkins is 29, in his absolute prime, and an alleged leader of the defense.

Yet Jenkins avoided ball carriers like they carried Kryptonite under their arms. Johnston is not in the habit of embarrassing players, but something as egregious as Jenkins’s effort demanded a breakdown, crackdown and smackdown. The unit that was universally lauded in 2016 is now ranked 31st in defense.

And that wasn’t the entire highlight reel on Jenkins. Read the scathing piece from NJ.com, which characterized Jenkins’ afternoon as a “no-show Triple Crown” and went into painful detail over three plays in which Jenkins whiffed, intentionally, to avoid contact. Or, as players sardonically assert, Jenkins made a business decision. In all, Jenkins whiffed on Hyde, on Garrett Celek, and Marquise Goodwin.

The same NJ.com piece pondered Jenkins’ future and whether the Giants will just cut bait on their all-world cornerback. Conveniently, Jenkins is not due another guaranteed dime after 2017, so the G-Men can jettison him with a more palatable $6 million salary cap hit after this season. And Jenkins is not the only one who should be looking for work in a new town.

Sorry. It’s really not your job, nor mine, to tell employers how to hire or fire employees. But the Giants are fully in collapse and rebellion. It speaks to the men hired to run the company. General manager Jerry Reese was hired to pick the players, and coach McAdoo was hired to make them play hard and well and with some measure of dignity. Pros should play and behave like professionals. The Giants do neither, giving up on plays and games, then are absent for team functions between games.

At least two players, ducking under the cloak of anonymity, said the team surrendered, that they don’t care or play with passion. They said, directly and indirectly, that the team has given up on the season.

There is no greater plight, slight or stain on a professional football player, than that of waving the white flag, of quitting, of a total disregard for the teammates, team and town. Bluntly, the Giants just don’t give a crap. And that falls entirely on the coach and the man who hired the coach. Between the historical proof that it doesn’t help and the Mara family’s gracious desire not to embarrass their employees, McAdoo won’t likely be fired before the season ends. But there is no reason for McAdoo — who makes Ray Handley look like Tom Landry — to begin 2018 as the Giants’ coach.

Big Blue is a blue-blood franchise, a proud member of the sport’s aristocracy, an NFL iteration of an Original Six squad. This stuff happens in Cleveland, in California, in Florida. Heck, it happens down the hall in MetLife Stadium, where the Jets have been the longest gridiron soap opera in syndication.

It doesn’t happen to the New York Giants. Until you hire Ben McAdoo. And things won’t get better until you fire Ben McAdoo.