It is difficult to imagine a more depressing few minutes than what the Giants experienced midway through the third quarter on Sunday. Rashad Jennings, starting to get on a running roll, had just been forced out with a knee injury and would not return. Eli Manning and Rueben Randle failed to connect on a third-down pass that sailed wide, forcing the Giants to punt the ball away. And then, three plays later, on third down for the Falcons, Antrel Rolle was too aggressive trying to contain a pass in the left flat to Antone Smith, hoping to stop the Atlanta running back short of a first down. Rolle took a bad angle, missed the tackle and Smith streaked up the left sideline for a 74-yard touchdown that gave the Falcons a 20-10 lead.

It was bad leading to worse, and the game was slipping away.

At the time, no one on the Giants sideline was thinking: “This is perfect. We’ll show how resilient we are, come back and win this game and it will serve us well later this season, because now we know we can do it.’’ But that is what happened, and the Giants will be able to hearken back to the 30-20 victory and what they did to score 20 unanswered points against the Falcons.

“It’s one of those moments you can point to at the end of the year and say, ‘Oh my gosh, look at what we did here and how that momentum carried us to the end of the season,’ ’’ Mathias Kiwanuka said.

A team that is serious about contenting for a playoff spot needs a game or two like this. It was the 26th time Manning has won a regular-season game after the Giants were trailing or tied heading into the fourth quarter. Even someone as accomplished as Manning needs a reminder of how to do it. The improving offensive line kept Manning clean most of the day and will benefit from the knowledge that it can hold up down the stretch when points are needed and then burn time off the clock once a lead is gained. The defense forced three straight three-and-outs (the last one was actually a four-and-out as the Falcons were sacked on fourth down), and that show of force will be recalled later in the season when a surge is needed.

The three-game winning streak has been assembled against three teams that probably will not find their way into the playoffs, but don’t discredit it. The Texans were unbeaten, the Redskins had the Thursday night home game scenario in their favor and the Falcons, though decimated by injuries on their offensive line, have weapons (and no ability to win under the bright blue sky). What comes next — road games against the Eagles and Cowboys — will tell a great deal about the direction this season takes before the Giants go off on their bye week. The Giants will not always play from ahead and will need a comeback or two along the way. At least they know they’ve done it before.

Other notables from the Giants’ victory over the Falcons:

— During the week, offensive coordinator Ben McAdoo expressed his excitement about Odell Beckham Jr.’s NFL debut, but cautioned, “We will take it slow with him.’’ Beckham had been mostly inactive for nearly five months with a strained right hamstring and had not made it through one complete practice, much less played a single snap in any NFL game, preseason or real season. Beckham was the last of the 32 first-round draft picks from this rookie class to play in a game.

Well, the Giants certainly didn’t take it exceedingly slow with Beckham, did not treat him like a china doll in need of bubble wrap. He was on the field for 35 of the 68 offensive snaps, just a notch more than 50 percent, exceeding the 15 to 20 snaps many predicted he would get. Beckham was in for 13 snaps in the first half and the workload increased after halftime as it was apparent his hamstring was holding up and he was running well. “I had something in the back of my mind,’’ Coughlin said of Beckham’s expected workload. “It seemed coming out after the first half we had that well in control.’’

— With Beckham finally on the field, Preston Parker’s playing time decreased. He received only 17 of the 68 offensive snaps. Parker more than made up for the season-ending loss of Jerrel Jernigan — Parker actually was an upgrade as far as production — and he caught three passes for 61 yards in his limited action against the Falcons. With Beckham moving in as the No. 3 receiver, Parker will get snaps when the Giants are in their four-receiver sets and every once in a while subbing for Beckham. It is also likely starters Victor Cruz and Rueben Randle, who rarely come off the field, will be given an occasional rest, with Beckham moving in on some two-receiver sets. He’s simply too talented to keep out of the game for very long.

— Now this is what’s called a demotion. Stevie Brown was almost never off the field in the first three games as the starting free safety, but has barely been seen since he was benched for Quintin Demps. He managed to get in for four defensive snaps last week against the Redskins. Brown didn’t get a single defensive snap against the Falcons, with Demps getting 71 of the 72. Demps has helped prevent big plays over the top, but he’s shown an alarming issue with ball security. He fumbled away a kickoff return earlier this season, and his latest bobble came after he intercepted Matt Ryan and was stripped of the ball on the return. The Falcons would have retained possession anyway — Prince Amukamara was called for holding on the play — but Demps needs to prove the ball is safe in his hands.

— The situation with Dominique Rodgers-Cromartie bears watching. The team’s top cornerback he was in for only 49 of the 72 defensive snaps, and when he was on the sideline, the trainers kept fiddling with his left ankle. Rodgers-Cromartie did not appear to run very hard or make much of an effort to chase on Smith’s 74-yard touchdown catch-and-run, and perhaps the ankle issue had something to do with that.

— After reaching unexpected fame as an improbable Madden video game cover boy back when he was rushing for 1,000 yards for the Browns, Peyton Hillis has settled into a reserve role, and he’s got a great attitude. He’s become a wild-eyed special teams tackler — at 250 pounds, he packs a wallop — and a role player on offense behind Rashad Jennings and rookie Andre Williams. Hillis got the first eight rushing attempts of his season last week mopping up in the rout of the Redskins and he got two more against the Falcons, giving Williams a rest after Jennings went down with a knee injury. Hillis can catch the ball out of the backfield and knows how to pass protect, which will be key as his playing time increases for however long Jennings is out.

— It is obvious and yet always remarkable to see the difference in the Giants when Eli Manning is not throwing it to the other team. He’s thrown only one interception in the three-game winning streak — and that one was pretty bogus, on a pass in Rueben Randle’s hands that easily could have been called a touchdown. Manning’s command of the new offense is growing every day, and the results are readily apparent. He’s had a passer rating above 100 (123.2, 117.5 and 104.9) in the three-game streak. It’s the first time that’s happened in three consecutive games since October 2010. How improved is the product? Manning had just one passer rating above 100 the entire 2013 season, and that came in the season-opening loss at Dallas.

— It’s been slightly less than five years since the Giants have been so prolific on offense. They’ve scored at least 30 points (30, 45, 30) in each of their last three games for the first time since December 2009, when they scored 31, 38 and 45 points against the Cowboys, Eagles and Redskins, respectively.