The Broncos’ franchise-record winning streak ended Sunday night at 17 in particularly violent fashion, with their star quarterback feted before the game and treated like a wedding crasher the rest of the night.

The patina of perfection fell away early. For all their Star Wars numbers on offense, to borrow a Jim Irsay phrase, the Broncos’ championship aspirations are as tenuous as anybody’s, especially if they keep letting pass rushers blast Peyton Manning from his blind side.

Before their 39-33 loss to the Indianapolis Colts, they had gone the equivalent of a full season plus a game since losing in the regular season, although even the streak felt less than perfect given the rather important playoff loss that came between the 11 wins that closed last season and the six that began this one.

For much of the streak, especially recently, the Broncos were so dominant that big themes seem necessary to explain the fact that they finally lost. The talk will be all about the soap opera, Manning’s return to Indianapolis and how he wasn’t quite himself while Andrew Luck, his successor, was.

Maybe it was the oddity of a 90-second tribute video to the opposing quarterback just before kickoff, which Manning felt obliged to acknowledge with emotional, heartfelt gestures.

Maybe it was the Colts’ decision — presumably owner Jim Irsay’s — to open the roof and the windows at one end, creating a chillier, windier environment than Lucas Oil Stadium normally provides for a visiting quarterback generally thought to be at his best when conditions are pristine.

Maybe it was the sack-fumble-safety when Colts defensive end Robert Mathis, a former teammate, crushed Manning from behind in the second quarter after leaving Broncos backup left tackle Chris Clark grasping at air.

“It was a good hit,” Manning said. “A healthy one, as I would call it.”

When a post-game questioner suggested his passes wobbled more after that, Manning grinned wryly.

“I throw a lot of wobbly passes,” he said. “Throw a lot of wobbly touchdowns, too.”

For all the echoes of ancient myths in the prodigal son’s return to the place his pro career started and the temptation to manufacture a moral from the outcome, the prosaic truth is the Broncos played well enough to win if it weren’t for a couple of critical mistakes.

Missing both of their starting offensive tackles, they struggled to protect Manning from the Colts’ pass rush. Manning was sacked four times, twice by Mathis. Two of Denver’s four turnovers — one fumble and one interception — came when edge rushers got to Manning before he could get rid of the ball.

Even so, they still had every opportunity to win if Ronnie Hillman hadn’t fumbled the ball at the Colts’ 2-yard line with three minutes to play and the Broncos down nine.

“I’d like to have seen it go to a two-point game down there toward the end and seen what would have happened,” Manning said. “It never quite got to that point, but you can go back to different parts of the game, and we got behind, and (made) mistakes there, but we still had a chance there at the end. So we did fight and hung in there. I think we can learn from it. We certainly have to improve from this game because we weren’t as sharp execution-wise as we’d like to be.”

On this point — the requirement to score twice there at the end — I’d like to highlight a fact likely to be overlooked. Call it a pet peeve if you like, but the arithmetic is indisputable:

If the Broncos don’t try a two-point conversion when they could have had a one-point conversion for free with a little more than 12 minutes left in the game, the difference later is eight points, not nine, and only one possession is required to tie, not two.

Teams are constantly making comebacks more difficult by going for two way too early. The index card that tells coaches when to go for two should be incinerated in a public ceremony and replaced with a much simpler one bearing these words: If there’s any question at all, take the free point.

The score was 36-23 at the time, following Manning’s 35-yard touchdown pass to Demaryius Thomas. The tortured logic of the two-point try is this: Two points cut the deficit to 11, meaning a touchdown, another two-point conversion and a field goal would be enough to tie. Take the one, you trail by 12 and need two touchdowns.

In the meritocracy of NFL play-calling, this line of reasoning is inane. With that much time left, you never know what’s going to happen. For example, Colts running back Trent Richardson might fumble deep in his own territory less than a minute later. The Broncos might recover and score another touchdown with nearly nine minutes still to play.

This, of course, is what happened. When the Broncos took the standard one-point conversion on the second score, they trailed 36-30. Had they taken the standard one-point conversion on the previous score as well, it would have been 36-31.

So the Colts’ field goal with six minutes left would have put them up eight, not nine. So, at the very end, the Broncos would have needed just one score and a two-point conversion, not two scores, as they did.

In short, going for two too early had exactly the opposite effect of what was intended, which is often the case.

Of course, even needing two scores, they had a chance, and a pretty good one, if Hillman hadn’t fumbled on a head-scratching running play at the Colts’ 2-yard line with three minutes left. Manning drove the Broncos offense 90 yards in six plays after being sacked to start the series, half of them sensational catches by Wes Welker. Needing two scores, there was no time to waste with a running play, and Hillman is not their best between-the-tackles option anyway.

In any case, if the Broncos score there, they’re within two, and Matt Prater’s field goal in the final minute wins it.

The Colts’ strategy in between probably changes, so who knows, but the bottom line is this defeat was largely self-inflicted. So much will be made of the soap opera that it will seem unsatisfying to suggest the outcome was mainly about three fumbles and one interception, but the outcome was mainly about three fumbles and one interception. Also a bad index card.

For all their mistakes, the Broncos had more first downs than the Colts (23-19) and more total offense (429 yards to 334). They gave up a likely touchdown on Hillman’s fumble, provided the Colts with a safety and set up an ensuing touchdown on the Mathis sack-fumble, set up another Colts touchdown when kick returner Trindon Holliday fumbled on his own 11, and set up a Colts field goal when outside linebacker Erik Walden hit Manning’s arm in the fourth quarter, producing an interception by inside linebacker Pat Angerer.

That’s 19 points for the Colts and minus seven for the Broncos as a result of their four turnovers. Without them, the Broncos win going away.

On the other hand, they weren’t just bad luck. Both Holliday and Hillman have had issues holding on to the ball before. I don’t know when Hillman next gets the call near the goal line, but I’m guessing it might be a while.

The other two are more problematic. On the sack-fumble-safety, Mathis beat Clark, who replaced the injured Ryan Clady, who is out for the year. Against capable pass rushers such as Mathis, the Broncos may have little choice but to routinely reinforce Manning’s blind side protection with a blocking tight end. That may limit some offensive options.

On the interception, Walden bull-rushed right through tight end Julius Thomas. NBC analyst Cris Collinsworth acknowledged Thomas’s ability as a receiver, but gave him low marks as a blocker.

Think of it as a cold shower for a team that’s heard hardly a discouraging word for the first six weeks of the season. The defense needs to get stouter and the ball security needs to get better. Mostly, the pass protection needs to improve if they want to keep Manning upright for the holidays.