The NFL achieved its time-honored postseason parity again with a one-third turnover rate among its entrants.

The Vikings are one of four teams to earn a playoff berth after failing to qualify last season. That ratio of fluidity has become standard.

Since the league expanded to a 12-team playoff format in 1990, at least four teams have made the playoffs in every season after not qualifying the previous year.

The Vikings also were in that position in 2012, their most recent postseason taste. But whereas that experience felt fleeting, almost fluky, the foundation for this playoff appearance seems sustainable.

The Vikings are positioning themselves to become a regular playoff team rather than one that merely pops up every so often.

The circumstances feel so different from those in 2012. That team required a herculean MVP performance from Adrian Peterson to secure a wild-card berth. Without Peterson’s near-historic season, the Vikings don’t make the playoffs.

They had Christian Ponder at quarterback and an aging and statistically average defense with an archaic scheme. Peterson masked their flaws with his remarkable campaign.

That formula was not viable over the long haul, as much as that term even applies in the NFL.

The infrastructure of the current operation provides more substance in projecting the future and feeling confident in the direction.

The team hired the right coach in Mike Zimmer, who has resuscitated the defense and changed the overall culture within the organization.

Improvement by the defense can be viewed in black-and-white terms. The Vikings ranked dead last in the NFL in scoring defense (30.0 points allowed per game) in 2013, Leslie Frazier’s final season as coach.

Zimmer has transformed the defense into a top-five unit in two seasons. The Vikings finished fifth in scoring defense this season at 18.9 points.

That, more than anything else, is why the Vikings are back in the playoffs. Championship teams play defense, and one can reasonably assume the Vikings will play high-level defense consistently under Zimmer. Or else the players found lacking won’t be part of his plans.

The change in culture is harder to articulate. It’s more nebulous, but the attitude at Winter Park just feels different. Everything seems more focused and self-assured and driven by a common purpose.

Zimmer took the job hellbent on making the Vikings a first-class organization that fears no challenge and accepts no excuse. That’s been refreshing, and it shows in the way his team plays.

A professional symmetry has developed among Zimmer, General Manager Rick Spielman and ownership. The group appears to be in lockstep on its vision and blueprint for constructing the roster.

That doesn’t mean they won’t make mistakes in the draft or free agency. No team bats a thousand in personnel decisions. But their plan makes sense. Build through the draft and develop talent.

The nucleus of the roster — specifically on defense — revolves around players who are either in their prime or still in the early stages of their careers.

The backbone of their defense is a group of players age 28 or younger: Everson Griffen, Anthony Barr, Harrison Smith, Linval Joseph, Xavier Rhodes, Sharrif Floyd, Eric Kendricks, Danielle Hunter.

Not a bad starting point with a defensive whiz in Zimmer at the controls.

On offense, Teddy Bridgewater is 23, Stefon Diggs is 22, Jerick McKinnon is 23, Kyle Rudolph is 26.

Bridgewater holds a large stake in this discussion. The organization’s future as a contender hinges largely on his development. We can all guess and speculate, but nobody knows for sure his true ceiling.

Bridgewater had a lousy performance Sunday night, marked by his bizarre decision to throw a lefthanded pass that was intercepted. He must play better.

But purely as a baseline, the Vikings won a division title in Bridgewater’s second season. It’s not a leap to suggest that he will continue to improve as he gains more experience.

Positive momentum cannot be overstated in evaluating the direction of an NFL organization. Look around the league this week as teams fire coaches, general managers and executives.

Change can feel invigorating, but change often means starting over with a plan that might not produce better results.

The Vikings have established positive momentum. They are division champions for the first time since 2009. Their new stadium is scheduled to open next season. A new, expansive team facility is in the works.

A playoff appearance for the first time in three seasons adds to that trajectory. They are taking the right steps to make this a habit.