In 1977, the Atlanta Falcons led the league in scoring defense.

They had two shutouts and held seven of 14 opponents to fewer than 10 points.

They allowed 129 points. Total. That's 9.2 per game!

And, oh yeah, they also went 7-7 and missed the playoffs.

The following year ushered in the 16-game schedule and sweeping landmark rule changes that planted the seeds for the passing game we see today.

The game changed dramatically. But the top scoring defense still has made the playoffs in 40 consecutive seasons since the Falcons fell short in 1977.

That streak could end with the Great Offensive Explosion of 2018.

Heading into Week 16, Tennessee and Baltimore shared the top spot in scoring defense at 18.1 points per game, which would be the highest by the top scoring defense in the Super Bowl era.

Both teams played Saturday. Tennessee beat the Redskins 25-16 in an afternoon game to move to 9-6 and take hold of the sixth and final AFC playoff seed, pending the Ravens-Chargers result Saturday night. Baltimore held the eighth spot at 8-6.

Rounding out the top five scoring defenses heading into Week 16 were the Bears (18.9), Cowboys (19.2) and Texans (20.1). Only Chicago has clinched a playoff spot.

Meanwhile, the top five scoring teams are the Chiefs (35.6), Saints (32.8), Rams (32.0), Chargers (28.2), Bears (27.4) and Steelers (27.4). Of those, only Pittsburgh has not clinched a playoff spot.

Numbers like those aren't pleasing to the eyes of a certain old-school defensive guy who wears a purple hat, works in Eagan and directed the top-scoring defense a year ago.

But Vikings coach Mike Zimmer isn't surrendering on behalf of his fellow defensive minds. Asked for the keys to keeping defenses relevant in a modern game governed by rules geared to handcuff defenses, Zimmer sort of shrugged.

"I think it's adjustments, really," he said. "You know, football has always been real cyclical. I go back to like Tampa 2, right? Everybody in the world ran Tampa 2 because the offenses couldn't figure it out. Then they figured it out and then everyone had to start doing something else. … Just like some of the double-A gap blitzes that we ran. No one could figure it out and then everyone started doing it.

"Everything kind of catches up to everything in time."

The key is to adjust as quickly as possible. Even in the Great Offensive Explosion of 2018, we're seeing signs of defenses making adjustments.

The Rams raced out to an 11-1 start and looked unstoppable with, as Zimmer says, "all the college influences with the rockets and all the things" coach Sean McVay was doing.

The signature game of the 2018 season was the Rams' 54-51 prime-time win over the Chiefs. Two weeks later, the Bears held them to six points. That began a two-week stretch in which the Rams scored 29 points and went 0-2.

Meanwhile, just as the Saints offense looked unstoppable, it was stopped. New Orleans had won 10 straight while scoring 40 or more points six times. The Saints went to Dallas, scored 10 points and lost 13-10.

Since those '77 Falcons missed the playoffs, the No. 1 scoring defense has won 11 of the 40 Super Bowls played. Another five have played in the Super Bowl.

The 2000 Ravens allowed the fewest points (10.3 per game) the past 40 years. And No. 2 isn't the 1985 Bears (12.4). It's the '86 Bears (10.6), whom history forgets because they lost their first playoff game.

Bill Belichick's fingerprints are on four of the top scoring defenses. Three of them led to Super Bowl wins, with the 1990 Giants (13.2) as defensive coordinator, the 2003 Patriots (14.9) and the '16 Patriots (15.6).

The other one, believe it or not, came during Belichick's five-year, sub-.500 run as Browns coach. In 1994, Belichick went 11-5 with a defense that allowed 12.6 points per game.

After that, the man who now owns five Super Bowl wins as a head coach won his first playoff game. Against Bill Parcells and the Patriots.

For the past four decades, having the best scoring defense has always punched a ticket to the postseason.

Will the streak end this year?

Mark Craig is an NFL and Vikings Insider. Twitter: @markcraigNFL. E-mail: