The harsh Christian Hackenberg truth is setting in

With regard to the mysterious two years of Christian Hackenberg, who’s one game shy of going through his first two NFL seasons without playing a single play in a real game …

… What must be going on in the mind of Jets general manager Mike Maccagnan, who by all accounts became so smitten with the former Penn State quarterback despite a poor finish to his collegiate career that he couldn’t be talked out of using his 2016 second-round draft pick on him?

… What must be going on in the mind of Jets coach Todd Bowles, who hasn’t shown any hint of wanting (agreeing?) to get Hackenberg into any games other than in preseason?

… What must be going on in the minds of Jets fans, who’ve been waiting since Ken O’Brien or Chad Pennington (or Joe Namath?) for a franchise quarterback to embrace?

… What must be going on in the mind of Texans head coach Bill O’Brien, who coached Hackenberg in his freshman year at Penn State, when he posted his best college statistics and looked like he was going to be revered the way Sam Darnold and Josh Rosen are today?

… Most importantly, what must be going on in the mind of Hackenberg, who (if he chooses to) can scan the internet searching for another 2016 second-round draft pick who’s gone the last two years without getting into a game and not find one?

The thought is preposterous, but it’s hardly out of the realm of possibility that Hackenberg might never take a snap in a real game for the Jets — or any other team for that matter.

Have you seen any evidence that might suggest otherwise — particularly with speculation running rampant about the Jets’ intention to draft another quarterback with their first-round pick this coming spring?

If the Jets do that, where does Hackenberg fall in the Jets’ pecking order of importance?

Further down than the oblivion where he’s resided these last two seasons, that’s where.

Hackenberg never playing for the Jets would be a damning blow to the reputation of Maccagnan, who was hired by Woody Johnson based on his ability to evaluate talent better than most.

After the Jets’ 14-7 loss to the Chargers on Sunday at MetLife Stadium, where Hackenberg actually warmed up on the sideline briefly late in the first half after Bryce Petty hurt his throwing hand, Hackenberg was asked how difficult it would be to take if he doesn’t get into Sunday’s season finale at New England and goes a full two seasons without playing a down.

“I can’t look at it that way,” Hackenberg said. “I think that’s a really negative way to look at it. I try not to look at it that way. It’s a waste of energy. I just need to continue to focus and be as prepared as I can for when that opportunity does come.’’

When or if?

That’s a more appropriate question.

“When your number is called you try and get ready,” Hackenberg said. “I try and stay locked in for the whole game. My job is just to be as prepared as I can for my opportunity when my number is called. One of the biggest takeaways I’ve learned in my two years here is to make sure every day you keep preparing and you keep learning, staying in it and understanding what you need to do to be able to take advantage of that opportunity when it comes around.

Josh McCown and HackenbergBill Kostroun/New York Post

“I approach practice the same way. There’s no differentiation between practices and games for us [quarterbacks].”

But the thing is: There is a difference. A big difference.

Playing in NFL games against opponents who want to hurt you and practicing against your teammates are as different as riding in one of those flight simulators at Disney World and actually flying a plane.

Bowles’ postgame answers Sunday when asked about Hackenberg, who’s become a punch line for Jets fans irritated by the fact that he was drafted so high and can’t get into a game, were curious at best.

When a reporter asked Bowles after the game what everyone else has been thinking — how bad must Hackenberg be if the coaches won’t put him in for the struggling Petty — Bowles actually said, “Christian is not that bad.”

“Not that bad.” That’s what you got with your 2016 second-round draft pick, Jets fans.

“When his time comes,’’ Bowles said, “it’ll come.’’

Unless it doesn’t.