What was shaping up to be a rousing victory devolved into what was about to become a demoralizing loss was shockingly reinvented as a stirring victory that the Giants earned — the hard way.

The Tommy DeVito way.

Trailing 22-21 after giving up a touchdown with 1:33 remaining, the Giants took over on their 25-yard line, putting DeVito in a position he had never before been in as an undrafted NFL rookie.

Go win the game, young man.

The pride of Cedar Grove, N.J., expertly directed an eight-play, 57-yard drive to set up Randy Bullock’s 37-yard field goal as time expired Monday night.

The Giants had a 24-22 victory at MetLife Stadium and DeVito added to his growing legend as the Giants’ Italian Stallion.

At the finish, DeVito was standing next to his head coach, Brian Daboll, who said he did not want to look as Bullock was lining up for a field-goal attempt that would determine if the Giants were going to rise or fall.

“At first he wasn’t going to look and then he was like, ‘I’m gonna look,’ ” DeVito said. “So we stood right next to each other. It was just pure excitement. I grabbed him, hugged him and told him I loved him.”

What’s not to love? The Giants are proud owners of a three-game winning streak and DeVito is moving from nice local-boy novelty act into a legitimate NFL quarterback who has a little something that is hard to define but easy to spot. His teammates get a kick out of him and want to play with him.

“The kid’s done a good job,” Daboll said, before adding, “I’m proud of him.”

Before the game-deciding drive — highlighted by DeVito’s impressive 32-yard strike to Wan’Dale Robinson — Daboll said he told DeVito to “go out there and rip that sonofabitch.”

It looked as if the Giants, leading 21-16, had the game signed, sealed and delivered when Saquon Barkley broke free on the right sideline for a 33-yard gain.

Barkley, though, shockingly tripped himself up, fell to the turf and lost the ball on the Green Bay 19-yard line.

Cornerback Carrington Valentine picked up the ball and, with players on the field momentarily stopped in their tracks trying to figure out what was going on, returned the fumble 50 yards to the Giants 36-yard line with 3:34 remaining.

“To be honest, I was running, I knew where the sideline was and was trying to make sure I didn’t go out of bounds in that situation and tried to fall down, and the ball just popped out on me, which is inexcusable,” Barkley said. “Got to be better. I can’t put my team in that situation.”

Jordan Love’s 6-yard touchdown pass to Malik Heath gave the Packers a one-point lead but they failed on the two-point conversion try when Bobby Okereke hauled down Jayden Reed.

“We had to go and make it tough on ourselves,” Daboll said. “Drive down with a rookie quarterback, make good decisions, nail a field goal with a new kicker. Probably like to do it the other way.”

It is the only way these Giants know how to do it.

They are 5-8 and one game out of the final wild-card slot in the NFC, although there are five teams with 6-7 records ahead of them.

DeVito finished 17 of 21 for 158 yards and a touchdown pass to Isaiah Hodgins.

He also gained 71 yards on 10 rushing attempts, as offensive coordinator Mike Kafka and offensive line coach Bobby Johnson suggested DeVito with his legs could exploit the Packers’ aggressive defensive front in the second half.

DeVito ran for 45 yards after halftime.

“That he’s a hell of a competitor,” Packers coach Matt LaFleur said, when asked what he learned about DeVito. “Certainly, we were running by him left and right, couldn’t get him.”

The Giants created two turnovers in the first half — a fumble by Love forced by Kayvon Thibodeaux and recovered by Xavier McKinney and an interception of Love by Jason Pinnock — and did not get any points off those takeaways.

Finally, in the third quarter, they cashed in on a turnover, this one coming on special teams when Darnay Holmes caused a fumble by punt returner Keisean Nixon, giving the Giants the ball on the Green Bay 31-yard line.

DeVito faked a handoff to Barkley and took off on a keeper, running 26 yards to the 1-yard line.

Barkley took it into the end zone from there for his second touchdown of the night to put the Giants ahead 14-10.

There was a strong defensive stand after a turnover on special teams — the ball hit off Bobby McCain covering a punt to put the Packers on the Giants’ 14-yard line.

A sack by Thibodeaux was instrumental in limiting the damage to a field goal to cut the Giants lead to 14-13.

It did not stay that way for long. On a flea-flicker — DeVito to Barkley — DeVito took a flip from Barkley and tossed 25 yards to Robinson.

DeVito on third down made a big-time play, rolling to his right to avoid pressure in the pocket and firing a perfect fastball to Hodgins, who leaped with Valentine in the right corner of the end zone and came away with an 8-yard touchdown grab to make it 21-13 late in the third quarter.

There were more highlights to come, for DeVito and the Giants.