When Peyton Manning threw an astounding 55 touchdown passes for the Denver Broncos in 2013, there was little doubt the team had made a sound decision to acquire the veteran passer a year earlier.

And after Andrew Luck transcended two years of lingering shoulder pain with a Pro Bowl season in 2018, the Indianapolis Colts looked as though they’d have an elite quarterback in place for many seasons to come.

If only the teams knew then what they know now.

In the ensuing years, both clubs learned about the massive challenges associated with replacing a franchise quarterback. In the process, they unwillingly became prime examples of just how formidable those challenges can be.

The Broncos rode the quarterback carousel for six seasons before landing nine-time Pro Bowl selection Russell Wilson in a trade this year. Meanwhile, the Colts are still seeking a long-term replacement for Luck, deploying new starters in each of the four seasons since he retired prior to the 2019 opener.

Neither team has won a playoff game since their franchise quarterback’s departure.

“In the end, it’s about a quarterback,” Broncos coach Nathaniel Hackett said at the NFL owners meetings in April. “You can ask all these [coaches] around here. You have to have a quarterback to have a chance.”

Quarterback consistency can be elusive in the NFL, but these teams -- who face each other Thursday in Denver -- enjoyed it while it lasted. The Broncos appeared in two Super Bowls, winning one, during Manning’s four seasons in Denver. And the Colts? They averaged more than 10 wins during Luck’s five full seasons under center.

But age quickly took its toll and forced Manning into retirement after the Broncos’ 2015 title. Luck, who replaced Manning in Indianapolis in 2012, was wary of more injury rehab after a lower-leg injury in 2019 and shocked the team with his stunning retirement announcement.

Both teams made numerous efforts to address the position, none particularly fruitful. They also tried bolstering their teams in other ways, especially on defense. But there are few substitutes for the ways in which a true franchise quarterback can change the trajectory and outlook of a team.

“The trade was game-changing,’’ Broncos general manager George Paton said of the Wilson deal. “It was game-changing for our locker room, the day-to-day, and for our football team … Anytime you get a franchise quarterback, a Super Bowl-winning quarterback like Russell Wilson, it’s going to accelerate anything that you’re doing.”

Colts coach Frank Reich knows this, too, but for a different reason: He understands the limitations on his team that result from the lack of quarterback continuity.

Reich has had a different starting quarterback in each of his five seasons.

“You’re always growing,” he said. “It’s like versions of software. There’s 1.0, 2.0, 3.0. And when you get a guy, you can get to further versions.

“Now, the software works a little better and is a little faster and there are new things that it can do … We know in this league the turnover rate is high at every position. But there are some core positions, quarterback being one of them, that just help you get to those future iterations and go deeper and further.”

There is much symmetry in the quarterback struggles of these two teams, but they arrived at their current junctures in very different ways.

The Broncos cycled through 10 different starting quarterbacks [running back Phillip Lindsay started a game under center during that span when the Broncos' quarterbacks were sidelined by COVID-19], not to mention three head coaches, between Manning’s retirement and the arrival of Wilson.

They tried the draft-and-develop route twice, trading up in the first round to select Paxton Lynch at 26th overall in 2016 and selecting Drew Lock in the second round (42nd overall) in 2019.

Lynch started just four games over two seasons. Lock made 16 starts over two seasons before being included in the Wilson trade. The Broncos traded five draft picks -- including two first-rounders and two second-rounders -- as well as three players to acquire Wilson and one draft pick.

A parade of veteran starters also came through town, a list that includes Case Keenum, Joe Flacco and Teddy Bridgewater.

But perhaps the most notable move is one the Broncos did not make. Bypassing quarterback Josh Allen in the 2018 draft still rankles fans in Denver, the team opting for edge rusher Bradley Chubb with the fifth overall pick instead. Allen was chosen seventh overall by the Buffalo Bills and this season looks like an MVP candidate.

The takeaway: Taking big swings at quarterbacks is great, but only if you swing for the right ones.

The Colts, on the other hand, have had veteran quarterbacks under center since Luck exited. Jacoby Brissett, Luck’s backup, took over in 2019. Philip Rivers signed as a free agent and started in 2020 before retiring shortly after the season. The Colts then traded first- and third-round picks to the Philadelphia Eagles for Carson Wentz in 2021, only to jettison him a year later in a trade with Washington. Now, Matt Ryan holds the job, but he’s 37 and has had a much rougher start to the season than anticipated.

The Colts’ boldest draft move for a quarterback in the past four years? Using a fourth-round pick on Jacob Eason in 2020. He was waived last year.

General manager Chris Ballard understands the boom-or-bust nature of drafting quarterbacks, which might be why he’s been hesitant about taking shots.

“Go back and look at first-round quarterbacks drafted over the last 10 years,” Ballard said last year. “It is not an exact [science]. Everybody just thinks you just take one and you’re going to fix the problem. Look, taking one will get y’all off my a-- for a little bit, but the second that guy doesn’t play well, I’m gonna be the first one run out of the building.”

Maybe there’s a lesson here, too: You can’t hit a home run if you never swing for the fences.

So, what’s next for these teams?

The Broncos have done the hard part by acquiring their franchise quarterback. Now, they have to find a way to maximize him. They are currently last -- by a wide margin -- in red zone efficiency (30%). Additionally, Wilson is completing a career-low 61.1% of his attempts. With a bit more time on task and more seasoning from their rookie head coach -- they’re only four games in -- the Broncos might well figure it out. And they’ll still need to navigate the loss of the draft and player capital they gave up for Wilson, something that should not be overlooked.

For the Colts, Ryan’s uneven start further demonstrates they’re likely on an unsustainable long-term path at quarterback. Even if Ryan were performing better, there still are consequences for the rapid turnover.

“It’s not an excuse, but every year we have a new quarterback. So we sit here and have growing pains while Tennessee has had [Ryan] Tannehill for what, my whole career?” Colts running back Nyheim Hines said after Sunday’s loss to the Titans. “Each year we’re restarting, and we have to turn the page. That sucks a little bit because most teams we play have had an established guy for a while.”

Those who do should enjoy it while it lasts, because life without a franchise quarterback can be a tough way to live.