Of all the possible outcomes following a brutal first half by the Bears on Sunday, the most preposterous was the one that had the Bears winning because of their sad offense. In second place was any outcome in which the Bears won, whether because of defense, special teams or asteroids.

The most-likely ending to the rainy afternoon figured to be no progress from quarterback Justin Fields, an inevitable loss to the 49ers and public shaming.

But something strange and wonderful happened at Soldier Field, something that surely seemed impossible to anyone who had watched that abysmal first half of football. A broken play led to a 51-touchdown connection between Fields and Dante Pettis. That led to a turbo-charged awakening by the Bears’ offense. And that led to a 19-10 upset in the bayou by the lakeshore.

It was Matt Eberflus’ debut as head coach, and if he chooses to remember it in its totality, he’ll be able to look back on the complete darkness of the first half followed by the bright light of the second half followed by a glorious light downpour. If he chooses to purge the first half from his memory, no one will blame him.

It’s difficult to do justice to the first half’s miserableness. Fields was 3 of 9 for 19 yards. He threw a bad interception and probably deserved to throw another. His passer rating was 2.8. The 49ers had 247 total yards to the Bears’ 68. This was a horse with two broken legs, and the humane thing would have been to put it down.

Oh, yeah, and this: On third-and-4 from his own 34 in the third quarter, new offensive coordinator Luke Getsy called a run play with the Bears trailing 10-0. No gain, but lots of boos at Soldier Field and lots of comparisons on social media to former head coach Matt Nagy, who had been guilty of similar crimes.

Everything looked the same, which is to say nothing looked different, which is to say, no, not this again. Just like last season, Fields wouldn’t have a chance because of his teammates and because of himself.

But then … something. That failed third-and-4 call? It was wiped out by a San Francisco facemask penalty. A few players later, under pressure from an extremely talented, extremely aggressive 49ers defense, Fields abandoned a play and scrambled to his left. It was there that he noticed Pettis by himself on the other side of the field.

“The vision by Justin to see that and throw it back there was a great play,” Eberflus said. “And that’s the kind of plays he can make. That’s what makes him dangerous because he can throw on-schedule throws, but, man, he’s got the off-schedule throws, too.”

“The ball felt like it was in the air forever,” Pettis said.

The result was that 51-yard TD play and a workable 10-7 deficit. Still, to the unbelievers (and you know who you and I are), the thought was, “Can an NFL offense be geared around broken plays, miscues by the opposing defense and a soggy field?”

O, ye and me of little faith.

From there, an energized offense took advantage of the hard work by the Bears’ defense, which would include an interception by the formerly missing Eddie Jackson. Fields hit receiver Equanimeous St. Brown over the middle for an 18-yard touchdown early in the fourth quarter. It gave the Bears a lead they’d never surrender, but more importantly, it gave the rest of us a look at what appeared to be an operational offense.

All well and good, but that first touchdown …

“That was kind of the play that changed the momentum of the whole game,” Fields said. “Once that play happened, that just kind of started everything else.”

The stunning victory was partly a result of San Francisco’s lack of discipline, which was weird because a lack of discipline was the Bears’ thing during Nagy’s tenure. The 49ers had 12 penalties for 99 yards. The Bears had three for 24. One of them was by holder Trenton Gill for using a towel to wipe down the wet grass before kicker Cairo Santos attempted a second-quarter field goal. I like to think of it as one last tip of the visor to Nagy.

Fields finished 8 of 17 for 121 yards and two touchdowns, with a rating of 85.7. Not great numbers, but after that first half, worthy of early Comeback Stat of the Year consideration — if, you know, there were such a category.

There’s work to be done. The offensive line played well in the second half but looked like it was going to be responsible for Fields’ early death in the first 30 minutes of action. And he needs to improve his decision-making. The physical attributes are there, but that’s not the most important thing about being a quarterback (see Tom Brady).

For one day, though, who cares? The 1-0 Bears, a team predicted to finish at the bottom of the NFC North, beat a Super Bowl contender.

“I’m not surprised,” Eberflus said of the victory.

Well, that makes at least one of you.