INDIANAPOLIS — If there had been a final defensive stop — always the biggest of “ifs’’ with the state of the franchise — Eli Manning on Sunday would have walked off the field at Lucas Oil Stadium — the site of Super Bowl XLVI, one of the two greatest moments of his career — on the winning end of a game he probably had no business winning in the first place.

Manning played well and gave the Giants enough production and points to shine some light on the darkness of this dreary season and, perhaps, give the “Keep Eli’’ crowd some additional talking points during debates at the holiday dinner table.

“He did a heck of a job,’’ coach Pat Shurmur said.

It was a heck of a job, but not a complete job. Manning, the lead the Giants owned for so long now gone, threw downfield in desperation and his 33rd pass of the day was intercepted by safety Malik Hooker with 23 seconds remaining, putting the finishing touch on a 28-27 loss to the Colts that adds to the misery of 2018 for a team that blew a game, again.

“It sucks, I’m not gonna lie,’’ rookie Saquon Barkley said. “I hate losing, it doesn’t sit well in my stomach. Everything happens for a reason, I’m a big believer in that. Once we get this thing figured out, and I believe it will be soon and we get this thing rolling we’re going to be playing at a high level and we’re gonna back and laugh on years like this.’’

No one is laughing now, not after what would have been an improbable upset instead dropped the Giants to 5-10 with yet another late-game defensive collapse. The Giants held leads of 14-0 in the first quarter, 17-7 at halftime, 24-14 in the third quarter and 27-21 in the fourth quarter but trailed, for the first time, after Andrew Luck finished off a tidy 53-yard drive with a 1-yard touchdown pass to Chester Rogers with 55 seconds remaining.

The Giants had one timeout to work with and needed about 40 yards to get in range for strong-legged kicker Aldrick Rosas. They got 11 on passes to Barkley (who failed to get out of bounds) and Evan Engram before Manning took a shot with a deep ball to Bennie Fowler that was picked off.

“Got to take a chance and get a chunk play,’’ Manning said.

“You got to take a chance there,’’ receiver Sterling Shepard said. “I don’t fault him for making that throw at all. We’re trying to get in field-goal range, that’s all we need and time is getting low. I don’t fault that decision at all.’’

A week after getting shut out, Manning was left without much of a running game to lean on — Barkley averaged only 2 yards a carry on his 21 rushing attempts — and put up 27 points without injured Odell Beckham Jr. A 27-yard strike to Engram and a 14-yard gain on an end-around by Engram helped the Giants, leading 24-21, get to the Colts 7-yard line but Manning got heat in the pocket and had to throw the ball away, forcing the Giants to settle for Rosas’ 27-yard field goal to increase their lead to 27-21 with 9:20 remaining. It turned out to be a fateful missed opportunity.

Still, this was a solid showing from Manning, who completed 25-of-33 passes for 309 yards, often taking advantage of play-fakes to Barkley to roll out of the pocket with movement that belies his age.

“I thought we threw the ball well,’’ Manning said. “I don’t know what all the stats were and everything, but maybe one or two I wish I had back. Besides that, I thought I threw the ball well and had a lot of good plays.’’

Manning also called his own number on a 1-yard quarterback sneak for a touchdown in the third quarter, only the seventh time he’s done that in his career.“He was spot on,’’ Shepard said. “He was hitting open guys, getting the ball out quick to guys and letting them make plays. That’s all you can ask for. He shows that all the time to me. It was nothing new. We just came up a little short.’’

They came up short because their defense, playing without injured starters Landon Collins and Alec Ogletree, could not get to Luck when he took over with 3:43 left, down six and needing a touchdown. Defensive penalties on rookie linebacker Tae Davis and cornerback B.W. Webb gave the Colts two first downs in what felt like an inevitable march to the end zone.

“We’ve got to get them stopped,’’ said Shurmur, who added “I don’t believe that narrative, fully’’ when asked if giving up late leads is a trend for this defense.

Luck was 31-of-47 for 357 yards. The Colts (9-6) have now won eight of their last nine games, a surge that turned a 1-5 start to into a credible playoff drive.

The Giants were left to board a flight after loss No. 10.

“We’re super close,’’ Shepard said. “We’re there. We just got to find out what the little things are and correct them. We got one more game coming up and try to put together a complete game.’’