The nature of the NFL, with a significant share of its small number of allotted games decided by a few key plays in close games, is for a great deal of parity from year to year.

The difference between 6-10 and 10-6 is much thinner, for example, than the difference between 62-100 and 100-62 in a regular Major League Baseball season. A bounce here, a missed or made kick there, an officiating decision everywhere separates the above-average from the below-average. Five of the 12 teams who missed the playoffs in 2018 made them in 2019. Among them was the Vikings.

Outside of that focused churn, though, we find larger truths about franchises: Periods of sustained success tend to be followed by relatively long periods of pain. Players get older. Trends change. And not even a salary cap ultramarathoner like the Vikings' Rob Brzezinski can outrun the cap forever.

History shows us some clear and symmetrical trend lines when it comes to the Vikings. Two very bad games into the 2020 season, the Vikings' play and the franchise's history conspire to make us ask: Are they in the midst of exiting one of their patented stretches of stability and relative success and rapidly entering one of their similarly familiar stretches of subpar play and rebuilding?

I should note first that I've been fooled by early struggles by a Mike Zimmer team, and I've generally vowed not to judge one of his teams until at least four games into season because they tend to get better with time.

These questions wouldn't be worth asking — at least not yet — if the Vikings' first two losses of the season were more pedestrian, couldn't-catch-a-break types of defeats. But the very nature of how the Vikings have seemingly been overmatched in every facet of the game makes this relevant now.

Two pieces of history first:

*From 1992 through 2000, the Vikings made the playoffs in eight out of nine years under Dennis Green, including NFC title game berths in 1998 and 2000. There were still high hopes in 2001, but that season quickly nosedived. The Vikings went 5-11 and Green was fired.

From 2001-2006, spanning three coaches (Green, Mike Tice and the first year of Brad Childress), the Vikings went 43-53, reaching the playoffs just once.

*But then from 2007-2009, the Vikings built to a crescendo. They went a combined 30-18 in the regular season, adding two wins to their previous season total every year, made the playoffs twice and reached the NFC title game in 2009.

2010? A plummet to 6-10, half of their win total in 2009, and the start of a five-year stretch spanning three coaches (Childress, Leslie Frazier and the first season under Mike Zimmer) during which the Vikings went 31-48-1 and made the playoffs just once.

*From 2015-2019, under Zimmer, the Vikings made the playoffs three times — advancing in the playoffs in both 2017 and 2019 — and went 50-29-1 in the regular season.

The surprise isn't that NFL teams like the Vikings suddenly go from contenders to bottom-feeders in the span of months. The surprise is that we don't know when it's going to happen.

We're only two games into 2020, but the trend lines are sure telling us what has happened and what could happen. The Vikings are hardly alone in this, but when they fall they sure seem to fall hard. And that sure seems like what is happening.

If that is what's happening, get ready for an ugly rest of 2020 — and probably a few seasons beyond as well.