USC's Sam Darnold, left, and UCLA's Josh Rosen could be...

USC's Sam Darnold, left, and UCLA's Josh Rosen could be the next Giants quarterback. Credit: Getty Images / Harry How

There may never be a more consequential offseason for the Giants and Jets than the one that is about to unfold.

With the coming week’s NFL Combine the next step in what will be a momentous roster re-shaping for both teams, the decisions made by general managers Dave Gettleman and Mike Maccagnan almost certainly will go a long way toward how these teams will look for years to come.

That’s not just hyperbole in advance of the scouting mission that awaits in Indianapolis, where more than 300 of the finest college players will convene to be examined physically and psychologically. That’s just the truth about two teams whose offseason moves will come to define their franchises.

There is never a more important time for any franchise than finding the right quarterback, and the Giants and Jets are simultaneously in that all-important phase. It is a situation that rarely has been seen in the more than half a century in which the teams have coexisted, yet a momentous time for both. And how they come out of the draft and free agency process will have a huge impact in their ultimate success — or failure — in the coming years.

With Eli Manning now 37 and in the twilight of his NFL career, the Giants must decide whether now is the time to draft his successor. Short answer: It is.

You don’t get the No. 2 overall draft pick very often — unless you’re the Browns, in which case you get it almost every year — and the only way the Giants don’t take a quarterback that high is if they’re convinced that Davis Webb is the answer. Last year’s third-round pick didn’t take a snap in the regular season, which makes the evaluation process somewhat complicated. But based on what new coach Pat Shurmur said in his introductory news conference last month, you get the sense that he doesn’t view Webb as the answer.

“We went through the process on Davis Webb, and we thought he was an outstanding player,” said Shurmur, who studied Webb when he was the offensive coordinator with the Vikings last season. “We liked how competitive he was. He’s got size. He’s got good arm strength. We felt like he was a guy worthy of being drafted and having a chance to be a starter someday. “

A starter someday? Unless Shurmur was being coy — and yes, there’s that chance, because no one in the league likes to tip his hand at this time of the year — the coach will have to seriously consider the top prospects this year. That means Sam Darnold of USC, Josh Rosen of UCLA, Josh Allen of Wyoming, Heisman Trophy winner Baker Mayfield of Oklahoma and Lamar Jackson of Louisville will be in the discussion moving forward.

There’s a school of thought that the Giants might be tempted to view Manning as being capable of lasting another three or four years. In this scenario, they would go after Penn State running back Saquon Barkley as a way of getting better immediately and worry about the quarterback down the road.

Bad thought.

You don’t use a pick that high on a running back when your quarterback is 37 and there are several prospects available without having to make a trade up the board. Just as the Giants had every intention of somehow getting Manning when they had the fourth overall pick in 2004, they now must be willing to take a quarterback at No. 2 . . . as long as they’re reasonably convinced that one of them is their guy.

Rosen has been mentioned most often as Manning’s heir apparent, but Darnold could be in the mix, especially if the Browns take Allen, as recent speculation has indicated.

Barkley can be a very special player in this league. But when the choice is a running back or a franchise quarterback, there really is no choice. It’s the quarterback every single time — unless, and only unless, you are convinced that not one of the passers is worthy of the second overall pick.

Gettleman is a sharp personnel evaluator and has been around long enough to know whether one of these quarterbacks is worth the pick. If he somehow bypasses all of them, you know he has serious enough concerns at every turn. If that’s the case, he’ll almost certainly look to trade down, given that quarterbacks are at such a premium in today’s NFL and a move down can net several additional picks.

The more likely scenario: He takes a quarterback (as well he should). Get a guy who projects as a top-flight passer the next dozen or so years, and the post-Manning question is solved.

It’s a little more complicated for the Jets, but not in a bad way. They’re actually in a strong position and might not even have to dip into the draft to come away with a big-time quarterback. As we’ve been saying for months now, the Jets’ best play is to sign Kirk Cousins as an unrestricted free agent and not be locked into taking a quarterback with the sixth overall pick.

Cousins is worth a megabucks contract because, at age 29, he can provide the answer at the all-important quarterback position for at least six years, which is plenty of time to continue building a quality roster around him. The Jets will know whether they can get Cousins well before the draft, and if they can beat out teams such as the Broncos, Browns, Vikings and anyone else bidding for his services, they’ll be in excellent position to either take an impact player at No. 6 or trade down and collect more picks.

Want to trade up to get a player like Barkley? That’s fine, too, because you’d have a big-time running back in addition to a highly capable quarterback who would represent a quantum leap forward. There’s no need to surrender a stockpile of picks to get Barkley, but if the price is reasonable for a move up, or if he somehow falls to the Jets at six, it’s in their best interests to take him.

The key, of course, is getting Cousins under contract, and that’s where Maccagnan must take an aggressive approach. Given that he’s armed with nearly $100 million in salary-cap space, that shouldn’t be too difficult.

Yes, important days are ahead for both teams. Days that could decide whether they’ll be able to talk realistically about contending for a Super Bowl someday — or continuing on a path to nowhere.