Anyone saying they saw this coming is dealing in untruths. Of all the shocking directions this season has taken the Giants, none is more harrowing than the way their defense has come off the rails.

“You tell me right now anybody on the team that’s playing well,’’ a Giants insider told The Post.

Well, um, sorry, no can do.

Steve Spagnuolo is a proven defensive coordinator, but he has been guilty of over-thinking with this group. He spoke of this season as “graduate school’’ for his guys, viewing what took place in 2016 as a commencement, of sorts, after expertly blending the old with the new. His unit finished in the top 10 in 12 important defensive categories, allowed the fewest touchdowns of any team in the league and the second-fewest points. The 17.8 points per game given up was the lowest figure for the Giants in 14 years.

There was every reason to think the defense was set, with the only significant loss — Johnathan Hankins to the Colts — mitigated by the arrival of Dalvin Tomlinson in the second round of the NFL draft.

“I just thought with the guys we had from last year and as well as we played defensively we could be even better this year, with another year in Spags’ system, more synergy, and I thought we looked really good in camp,’’ the Giants insider said. “I was very buoyed by Jason Pierre-Paul, just the way he competed in camp. He was hustling like a rookie, a new sense of fervor. I thought at the end of last year we had to be very pleased how Eli Apple got better and better. I thought defensively the arrow would be up.’’

And now?

“Defensively we haven’t made a play,’’ the insider said. “JPP hasn’t made a play, Olivier Vernon’s beat up. Landon Collins hasn’t made a play. Eli Apple has regressed.’’

Spagnuolo thought he could dig deeper into his bag of tricks and, as the big plays piled up, like autumn leaves in the backyard, the outcry was to simplify. At best, the players in the secondary are confused. At worst, they are indifferent.

The Giants, since records have been kept, never allowed two touchdown passes of at least 47 yards in back-to-back games, which happened against the Rams and 49ers, with scoring passes of 52, 67, 47 and 83 yards.

The downward arc to Collins’ career is the greatest mystery, as a case could be made he was the best safety in the NFL in 2016. It is as if Collins this season is in a perpetual state of hesitation. He unfailingly offers public support for Ben McAdoo, and for the most part steered clear of criticizing suspended cornerbacks Dominique Rodgers-Cromartie and Janoris Jenkins. Collins wants to be seen as a leader, yet does not want to step out of his comfort zone to do so.

Damon Harrison is a force against the run; opponents know this and often attack on the outside, where Snacks does not eat. Tomlinson is a keeper but he is a rookie. For what they re-signed him for (four years, $62 million) the Giants are not getting what they need out of Pierre-Paul, and Vernon’s season has been marred by a sprained ankle. At best, the linebackers were a stop-gap group but injuries to Jonathan Casillas, Devon Kennard and Keenan Robinson forced undrafted rookies to start, which is never a good thing. In the middle, B.J. Goodson had a brilliant NFL starting debut in Dallas but has barely been seen since, with shin and ankle issues delaying his development.

“He has a chance to be a really good NFL player and a real find in the fourth round,’’ the insider said, “but your value is determined by your availability and he hasn’t been available.’’

The three (Vernon, Jenkins and Harrison) big-ticket free agents in 2016 fit like a glove, none more snugly than Jenkins. Year No. 2 is a different story. He remains the team’s top cornerback but is not consistent. His no-show and then no-call to explain the no-show coming out of the bye week was out of character, and he came out of his suspension with a no-show effort against San Francisco, all of which is quite troubling.

An NFL source said Jenkins did not give the Giants much of an explanation for why he failed to show up for work and that he was actually in New Jersey when he decided not to attend practice.

“The whole thing sounded terrible to me,’’ the NFL source said.

After this season, all of Jenkins’ $29 million in guaranteed money will be paid to him.

“They can release him, the cap hit means nothing, they can release him and they’re good,’’ the source said.

It would be stunning if it came to that, but everything about this defense, and this season, has been stunning.