SEATTLE — At halftime, Brian Daboll walked into the visitors locker room and gave his version of realty.

The Giants were playing well, strong, resilient.

At times in the first 30 minutes Sunday, they had dominated the Seahawks, which is not easy to do to them in their own noise-drenched building.

And yet, the game was tied at 10 and a familiar script was in the works for a team that has yet to prove it knows how to win.

“Honestly, Dabes came in here yelling at us, saying we can’t be doing the bulls–t that we were doing,’’ Dexter Lawrence said. “It wasn’t a lot of praise, it was more let’s dig in and finish this game. He was a little more fired up than normal. That was good, we fed off it and kept balling.’’

Daboll felt it.

His team had a chance to pull off the upset but the Giants had to raise their level of play.

They did it, building a 10-point lead early in the fourth quarter.

Down the stretch, though, the margin had narrowed to a field goal and Seahawks kicker Jason Myers was lining up for a 47-yard field goal with 55 seconds remaining.

Overtime beckoned.

Until an unlikely player made a play to remember.

Isaiah Simmons, relegated to special teams duties, rose up and blocked the kick, sending the ball to the turf, where Bryce Ford-Wheaton scooped it up and sprinted 60 yards for a game-sealing touchdown, turning tension into exhilaration.

The Giants went far from home and came away with a 29-20 victory at Lumen Field.

“He made a helluva play at the end of the game to seal it,’’ Daboll said not long after he awarded Simmons with a game ball.

“Just being able to go out there and, s–t, call it what it is, win the game for the team, shoot, it felt good,’’ Simmons said.

This was some team victory, considering who was not part of it and who carried the load.

The Giants (2-3) did it without Malik Nabers, their rookie sensation wide receiver, and without starting running back Devin Singletary.

They had to improvise on offense, and Daboll did so with aplomb, trusting youngsters who had not done much in the first four games.

Rookie running back Tyrone Tracy in his first NFL start gained 129 rushing yards and a tight end — rookie Theo Johnson — was actually a part of the passing attack.

Daniel Jones, orchestrating with high efficiency, tossed touchdown passes to Wan’Dale Robinson and Darius Slayton (eight catches for 122 yards filling Nabers’ spot) and did not turn the ball over.

On defense, the Giants got to Geno Smith, sacking him seven times — three by the menacing Lawrence. Deonte Banks did a fine job dealing with DK Metcalf (4 rec., 55 yards) and running back Kenneth Walker (5 carries, 19 yards) was a non-factor on the ground.

“It’s our second win,’’ Daboll said. “Certainly we’d like to have more. But we don’t.’’

If the Giants can continue to get contributions up and down their roster, they might be able to.

The third of Greg Joseph’s three field goals put the Giants ahead 23-13.

The Seahawks responded with a 14-play, 95-yard drive and when Smith hit Jaxon Smith-Njigba on a 5-yard pass with 2:09 to play, the Giants lead was trimmed to three points.

The offense could not keep possession and the Giants had to punt it away with 1:40 left.

Smith’s 32-yard run set Myers up and special teams coordinator Michael Ghobrial dialed up a special field goal block play, featuring Simmons’ leaping ability.

He did a double-jump to swat the ball out of the air and that was that.

With Nabers back home in New Jersey, still in concussion protocol, Slayton turned into a big-play target with an over-the-shoulder grab for 41 yards and then a 30-yard touchdown catch to put the Giants up 17-10 early in the third quarter.

Meanwhile, Tracy was muscling for yards.

He came into the game with 12 rushing attempts and 29 yards but he was a workhorse as the fill-in for Singletary, who was out with a strained groin.

“We’ve said since training camp how much we like our skill guys and how deep we think those positions are,’’ Jones said. “You saw a lot of guys step up and make a lot of plays. When we say that we mean it. We have a lot of confidence in those guys. You know, they stepped up and played very well.’’

The way it started was almost incomprehensible.

Second-year running back Eric Gray, on fourth-and-goal from the 1-yard line, tried to leap his way in, was stopped short of the goal line and lost the ball on a hit by linebacker Jerome Baker.

The ball deflected into the end zone, where safety Rayshawn Jenkins was there to scoop it up.

For a moment, everyone froze — everyone, that is, other than Jenkins, who raced the ball out of the end zone and almost casually sprinted down the field, with no one in pursuit.

He walked in for a 101-yard fumble return for a touchdown and all that good work by the Giants resulted in heartache and a 7-0 deficit.

To their credit, the Giants did not allow that colossal momentum swing to deter them.