DENVER — A rough start. A series of ups and downs. Adversity. Perseverance. Perseverance. Belief. A gradual rise. A fantastic finish.

Is that the story of the Case Keenum’s day on Sunday or the story of his career?

As the Denver Broncos’ new quarterback led the team to their second come-from-behind victory in as many weeks, and their biggest second-half comeback since 2012, it was hard to ignore the similarities in the storylines.

You can’t keep Case Keenum down. Adversity is his favorite opponent. This is nothing new.

There’s no other way to slice it, the first half for the Denver Broncos felt like a fever-dream flashback to 2017. Unfortunately, that was just the hottest home game in Broncos history mixed with some hot-garbage offense. In that time, Keenum was anything but sizzling, going 5-for-11 for 38 yards and an interception.

Fresh out of the break, though, Denver’s most-prized offseason acquisition began his resurgence, leading the team on an 11-play, 75-yard scoring drive to make it a game all over again.

His next possession? 10 plays, 54 yards, field goal.

The next? 14 plays, 77 yards, capped off with a one-yard rushing touchdown by the QB on a do-or-die fourth-and-goal.

Score, score, score was one helluva bounce-back after going punt, punt, punt, interception, punt in the first half. But the abysmal start meant all of that wasn’t enough, it all came down to the final drive.

Down two, with one minute and 52 seconds left on the clock and zero timeouts in his pocket, Case Keenum walked into the Broncos huddle with a simple message.

“Let’s go, men,” left tackle Garrett Bolles said, recollecting the moment.

But it wasn’t the words that resonated as much as his demeanor.

“Calm,” explained Jake Butt.

“He is a calm, composed person, man,” added Bolles.

He’s been there, and that calm, cool composure told the men in the huddle everything.

“We all knew,” Bolles said. “We all knew we were going to win the game.”

With a soft-cushion defense in front of him, Cool Hand Case took what the Raiders were conceding all the way down the field. 21 to  Emmanuel Sanders, 14 to Butt, four to Jeff Heuerman and, finally, the kill shot, 26 to Tim Patrick, setting up Brandon McManus for a 36-yard field goal with 10 seconds left.

As he handed the reins to McManus, though, Keenum savored a long, slow strut off the field.

“I took a second,” he said. “Just enjoying that moment, knowing me and my teammates are all bloody, we’re all hurting, but we walk off the field knowing we left it all out there. Every single guy in the locker room did that today.”

As everyone expected, McManus drilled it. Broncos win.

In all, Keenum went 15-of-24 for 184 yards and a rushing touchdown in the second half.

“Adversity punched us in the mouth,” Bolles said, describing the team and, more appropriately, his quarterback, “but we turned around and punched it right back.”

“We believe in number four,” he concluded.

Welcome to the Case Keenum story: A rough start. A series of ups and downs. Adversity. Perseverance. Perseverance. Belief. A gradual rise. A fantastic finish.

That guy should write a book.