Nearly four years ago, on the sunny, March day that saw Peyton Manning introduced as the newest member of the Denver Broncos, a Mile High Sports Radio host asked a question that will forever encapsulate No. 18’s era in the Mile High City. As John Elway stood at the podium and fielded questions, Lisa Snyder asked, “What’s plan B?”

Stumped a bit, the Broncos general manager thought for a moment. Then, he offered an answer that would go on to define the team’s all-in approach during Manning’s time in orange and blue.

“We don’t have a plan B,” Elway said, smirking like a poker player who was pushing all of his chips to the middle of the table. “We’re going with plan A.”

And for the last four seasons, that’s exactly what Denver has done; they’ve put everything they’ve had behind a Manning-led team, looking to ride one of the all-time greats to another Super Bowl title. The end result came just eight days ago, when the Broncos captured their third Lombardi Trophy with a 24-10 win over the Carolina Panthers.

Most people saw Super Bowl 50 as the perfect ending to this chapter of team history. Manning could ride off into the sunset as a champion, with his next stop being an induction ceremony five years from now in Canton. And the Broncos could turn the page, having rolled the dice on a quarterback coming off of four neck surgeries and winning big with a world championship.

It’s the perfect storybook ending. Or so everyone thinks.

As the Broncos turn their attention from winning a Super Bowl to defending their title, something ironic has occurred. Manning has become plan B.

Most people assume that Brock Osweiler will Denver’s starting quarterback next season; after all, he led the team to some big wins during a seven-game stint in 2015. But him becoming the heir apparent is far from a sure thing.

After spending the past four years as Manning’s apprentice, Osweiler is a free agent; he can sign with any team, making his services available to the highest bidder. And that makes it a very real possibility that the team’s long-time “QB of the future” will be elsewhere next season.

The NFL’s free agency period starts a month from today. The Broncos have made it known that they’d like to keep the quarterback that they’ve groomed for the past four years. Osweiler has said that he’d like to stay in Denver, taking over a team with championship mettle.

But those intentions could easily be derailed. Elway and Company will be busy during the first few weeks of the offseason trying to keep their defense intact; keeping Von Miller, Malik Jackson, Danny Trevathan and Brandon Marshall on board are the No. 1, 2, 3 and 4 priorities of the team. At the same time, Osweiler will be tempted by the chance to earn more money in another city.

Four years ago, Matt Flynn got a three-year, $26-million contract from the Seattle Seahawks on the strength of a one-game performance with the Packers. So it should come as no shock if another team that thinks it is on the cusp of competing throws a hefty offer Osweiler’s way after just seven career starts.

Houston and Los Angeles are playoff-caliber teams in need of a quarterback; they might break the bank for No. 17. And Cleveland is starved for a steady signal caller, making Osweiler a viable option there, as well. All three teams have a ton of cap space, making it possible that they can outbid a Denver team that has other priorities when it comes to spending money.

If that happens, the Broncos are in a bit of a pickle. Suddenly, the defending Super Bowl champs are without a starting quarterback.

Sure, Elway could try to find a stopgap option via free agency; but it’s hard to get excited about the prospect of Sam Bradford, Chase Daniel or Brandon Weeden lining up behind center for the league’s opening game on Thursday, Sept. 8. And even if Robert Griffin III or Colin Kaepernick hit the open market, they’d be risky gambles to say the least.

Which brings about plan B. Should Osweiler leave town, the best option for the Broncos is Manning.

Of course, that’s assuming No. 18 wants to play another year; that remains to be seen. But just because everyone else thinks he should retire doesn’t mean that Manning agrees; he’s a football rat, a guy who can’t get enough of the game. And he’s smart enough to know that once he stops playing, that decision is forever; there’s no coming back in a year or two when boredom sets in.

Thus, he may be tempted to give it one more shot; there has to be a part of him that will find it hard to walk away from a team as talented as the Broncos. And there’s still plenty to accomplish.

While Manning proved to be a great teammate after coming back from a foot injury late in the season, he can’t be thrilled that his final three games were spent handing the ball off and running the clock; the desire to show that he can still play has to be there. A much improved offensive line, with Ryan Clady (if they restructure his contract) and Ty Sambrailo back from injury would give Manning the chance to do just that; Denver’s inability to protect the quarterback was the No. 1 reason they were so conservative at the end of the season and during their playoff run.

Plus, there are still some numbers to chase. Currently, Manning is tied with Brett Favre for the most career regular seasons wins by a starting quarterback with 186; one more victory would put him atop that list, while also keeping Tom Brady’s pursuit of that mark (the Patriots QB currently has 172) at bay. And a third Lombardi Trophy would give No. 18 the championship edge when the Mannings gather for family events, putting Peyton one ahead of Eli in that department.

In order for Manning to return, however, he’d have to take a significant pay cut; there’s no way the Broncos can afford the $19.5 million he’s scheduled to count against the salary cap next season if they hope to keep their championship defense mostly together. But he might be willing to do that; playing another season would be about everything other than the money.

Denver could release Manning prior to March 9, which is when his 2016 contract becomes guaranteed, and take a $2.5 million cap hit for the prorated signing bonus he took home last year when he restructured his deal. Then, they could sign him to a new deal worth $4 or $5 million, the type of dough it will take to land someone like Daniel or Weeden, and draft someone to compete with Trevor Siemian next season. That gets Manning’s total cap number well below $10 million, allowing the Broncos to keep a title-contending roster around him.

All of which means the clock is ticking for Osweiler. While the quarterback isn’t slated to hit the open market until March 15, his deadline with the Broncos is really a week prior to that date. Because on March 8, Denver needs to decide if they need to go in another direction; if a deal with Osweiler isn’t done, Manning will be the only viable option Denver has remaining.

Who would’ve thought that the answer to the question was right there in front of everyone all along? As it turns out, Peyton Manning might be plan A and plan B.