This is a line-of-demarcation game for the Giants.

They’ll play the Cardinals on Sunday at MetLife Stadium as close to full strength as they’ve been in weeks, with running back Saquon Barkley and tight end Evan Engram back from injuries.

They’re merely a game out of first place in the mediocre, up-for-grabs NFC East — which is somewhat amazing considering their 0-2 start, quarterback change and rash of injuries.

This game represents a fork in the road for the Giants.

If they take the right route and win, it might be a sign they’ll be in this thing for the long haul, contending for a playoff berth until the end.

If they take the wrong route and lose, this season likely morphs into the Daniel Jones Developmental Tour, with win-loss results taking a back seat to the growth and experience of their rookie franchise quarterback.

With a win over a 2-3-1 Cardinals team they should beat at home, the Giants would be 3-4, winners of two of their past three games. And they would remain a game behind either the Eagles or Cowboys (who play each other Sunday night) for first place in the division with nine games remaining.

A loss to the Cardinals, and the Giants would slip to 2-5, having lost their past two games, and this season would become all about developing Jones.

The Giants’ mantra this season has been about rebuilding on the fly while winning along the way. Sunday represents a show-us game in that regard.

Coach Pat Shurmur’s theme to his players has been clear in that he has urged them to avoid looking at anything other than the game in front of them. For example, talk about their fortuitous situation in the division with the Eagles and Cowboys having their own personal crises is forbidden.

“We don’t do that kind of math,’’ Shurmur said after Friday’s practice. “It’s a dangerous thing to do. So, I encouraged our players to stay in the moment, be where your feet are. That’s how you have to play this thing. Let other people do the math.’’

The schedule math is simple. If the Giants beat the Cardinals, the worst they’ll be is still one game out of first place in the NFC East.

They’ll trail either the Cowboys or Eagles by a game and be tied with one of them.

The roster math is encouraging, with Barkley back after missing the past three games with a high ankle sprain and Engram back after missing the game against the Patriots with a knee injury.

“What a wonderful way to get back on track — at home with the offensive weapons that we have [returning], and to get back on track and try to make a run,’’ center Jon Halapio said Friday. “We’re very excited to be that explosive offense that we aim to be.’’

In his first two starts, Jones was without receiver Golden Tate, who was serving an NFL suspension. Barkley sprained his ankle in the first half against the Buccaneers, Jones’ first NFL start, and hasn’t played since. Receiver Sterling Shepard (who’s still out on concussion protocol), Engram and No. 2 running back Wayne Gallman all missed the last game, a loss to the Patriots on Oct. 10.

Sunday will be the first time Jones has played with Barkley, Engram and Tate.

Halapio, while conceding the opportunity to be so close to the top in the division “is very energizing and very encouraging,’’ was quick to add, “Once we start focusing on that, then we lose focus on winning the games that are at hand. How we control our destiny is by winning.’’

Surely music to Shurmur’s ears, knowing his message is resonating inside the locker room.

There were more sweet sounds to Shurmur’s ears from Tate, who said: “I try not to even think about where we are in the division, because if we don’t win then it doesn’t really matter what happens in the division. We’re trying to chase greatness.’’

And more from safety Michael Thomas, who said still being so close in the division “is great that it’s there with everything considered — us not starting the way we wanted to start and not having the results we wanted — but at the end of the day, we’ve got to go out and win.

“This is our season, this is our opportunity to go out there and show what we can do. This is a huge opportunity for us. It’s all in front of us.’’

Once it’s not in front of the Giants, which could come as soon as Sunday with a loss, then this becomes less about results and more about Jones and a look to the future. And no Giants fan is ready for that just seven games into the season.