The Vikings will use their fourth starting quarterback on Saturday, in the 14th game of their season, when Nick Mullens takes their first offensive snap, and maybe several more.

At this rate, the Vikings will be cooking up a special play on Jan. 7, when they face the Detroit Lions for the championship of the NFC North: Sean Mannion will take the snap from center and pitch to Joshua Dobbs, who will hand it to Joe Webb or Spergon Wynn or Case Keenum.

What's more remarkable? That the Vikings, comfortable with Kirk Cousins' remarkable durability entering the season, are on their fourth starting quarterback? Or that they are on their fourth starting quarterback and are in position to make the playoffs and perhaps even play for a division title?

We have relearned a few NFL verities this season:

• Every durable quarterback is one bad step away from spending the season doing ManningCasts and shopping at Kohl's for the perfect sit-around-and-do-nothing Pima cotton mock turtleneck.

• The second-most important position on the roster might be the backup quarterback. (Or fourth quarterback.)

• The NFL can quickly become unwatchable when the position isn't played well. Exhibit A: Dobbs vs. Aidan O'Connell. Which is why every new rule devised to protect quarterbacks is a good idea, even if your buddy who starred at linebacker for his JV team in high school thinks they ruin the sport.

• We cannot overstate how difficult it is to succeed long term at the most difficult position in sports.

Vikings coach Kevin O'Connell's draft résumé listed him as 6-foot-6 and 228 pounds with a strong arm.

He's tall, athletic and intelligent. He proved his mastery of offensive coaching as the offensive coordinator of the Super Bowl champion Rams and while guiding the Vikings to 13 victories in his first season as a head coach.

Dobbs studied aerospace engineering. He's experienced and athletic and possesses leadership characteristics.

O'Connell was allowed to throw six NFL passes. Dobbs can't hold on to a starting job, and after his collapse this season, he may have trouble landing a job as a backup next season.

That's how hard playing quarterback in the NFL is.

Being smart isn't enough. Being large and athletic isn't enough. To succeed as an NFL quarterback, you have to understand what every player on offense is doing or needs to do, and what every player on defense intends to do. You need to memorize a playbook longer than the unabridged scripts of every episode of every version of "Law & Order."

You need to be nimble enough to avoid 280-pound defensive ends who run like Olympic hurdlers, strong enough to gun passes past cornerbacks on the far sideline, and accurate enough to sling an oblong ball through what might as well be a rolling Hula-Hoop while large bodies roll into your ankles.

There's also a catch to the position: If you do all of the above well, you will not receive due credit unless your team wins.

The position has never been more complicated or difficult to play, but if you're Dak Prescott or an efficient passer like Cousins, your production will be disregarded if you can't elevate your franchise.

Vikings defensive coordinator Brian Flores has excelled this season at dominating lesser or inexperienced quarterbacks. That skill will be required Saturday when the Vikings face Bengals backup and former Vikings project Jake Browning.

Asked why the quarterback position is so difficult and demanding, Flores said: "There's a number of reasons. That guy has to be a leader and the face of the franchise. There are expectations that come with that. From a football standpoint, he is required to have a general understanding of the entire offense. Every position. Make sure they're lined up right and in the right position, have to get the cadence right and see the defense so you can get into a good play, or at least a better play."

According to ESPN, no NFL team has ever lost its starter for the season, started three other quarterbacks and made the playoffs. Saturday, Mullens will try to give the Vikings a fourth victory from a fourth starter in a seven-game stretch, something never done before in a non-strike season.

"There's a lot that goes into that position," Flores said. "And there's a toughness aspect to the position, just because you're taking a lot of hits. You have to be mentally tough. It's a difficult position, and we try to make it a little harder, if we can."