The countdown to the regular season will be reduced to 13 days Monday. And some time within the next 13 days, the Giants will make Odell Beckham Jr., No. 13, the highest-paid receiver in the NFL.

Here’s why you can take a Beckham deal — ballpark $90 million — to the bank.

It will get done because general manager Dave Gettleman’s Big Blue Blueprint is ruined without one.

And when a Beckham deal is struck, do not underestimate the role Pat Shurmur will have played in the rapprochement.

The hiring of Shurmur has proven key because it has helped encourage Beckham to play ball with the Giants.

He has a head coach who has gone out of his way to establish a relationship with him, a respected offensive mind and a head coach Beckham believes can help him become legendary.

The Giants in kind have played ball with Beckham.

A win-win is on the horizon … and some sort of hometown discount on Beckham’s part, even as a token gesture, would go a long way toward cementing the marriage between franchise and franchise player.

And if you think it is mere coincidence Beckham will have not played a single snap in the preseason, think again.

Shurmur’s first face-to-face sitdown with Beckham came at a convenient time, when the newly hired head coach was working out the quarterbacks the Giants did not love the way they loved Saquon Barkley.

“It was just part of getting to know all the players, and especially Odell at that time,” Shurmur said.

He was asked what was so fruitful about that talk.

“It was just one of the initial conversations I had with him in terms of just getting to know him,” Shurmur said. “And certainly at that time, we couldn’t really talk football. It was just me getting to know Odell and him telling me about his family and who he was and what he was looking for. It was more of just a social visit.”

This is the way of the sports world nowadays. David Fizdale visits Kristaps Porzingis in Latvia. Beckham, rehabbing that fractured ankle, didn’t require a mandatory minicamp to show up at Quest Diagnostics Training Center this offseason.

“It’s a coach-player relationship where we’re working with one another,” Shurmur said, “with the idea that I’m gonna try to help him become the best he can be.”

Asked how many times he met or spoke with Beckham, Shurmur said: “Frequently. Very frequently.”

Shurmur has learned the very thing Tom Coughlin and Ben McAdoo always knew about Beckham.

“You want a guy that loves to play the game, and that’s who he is,” Shurmur said.

The Giants drafted Barkley over Sam Darnold in part because they believe they can win now with 37-year-old Eli Manning.

But in order to have a chance to win now, a long-shot chance in the eyes of many, they had to be convinced Beckham received what was essentially a Shape Up or Ship Out ultimatum in March from John Mara.

And they know they have to sign him in the next 13 days to prevent a dark-cloud distraction from complicating matters for their first-year head coach.

Signing Beckham — immensely popular with teammates — will launch the Giants into the regular season on an emotional reminder that ownership and management are committed to winning now.

Reading the tea leaves, it is logical to conclude a secret deal was struck in private between Beckham and the Giants regarding preseason games: Beckham would not be playing in them in the absence of an extension.

The code words were spoken early and often over the summer by Shurmur: “We’ll be smart with him.”

Smart, of course, is not subjecting your best player coming off a fractured ankle to a meaningless game played sometimes by overzealous defenders looking to impress their coaches and maybe even fighting to keep their NFL dreams alive.

Largely because of the trust established over the offseason between Beckham and Shurmur, there would be no holdout that would be a dark cloud hovering over the new head coach’s first training camp.

The stakes were and are too high for both sides.

It has been proven so far that the Giants can lose with Beckham and lose without Beckham.

But they have zero chance to win without Beckham.