Numerology is the belief in a mystical relationship between a number and coinciding events. And I’m a believer in the mystical power of “Eight’’ when it comes to Minnesota’s NFL franchise.

The Vikings open a 58th season on Sunday vs. San Francisco in the Taj Ma Zygi. And the history with Eight assures us that it is going to be a landmark season — as in an important stage or turning point — for the Purple.

There have been five previous Seasons of Eight and all dramatic for varied reasons:

EIGHT WAS ENOUGH (1968): The Vikings went 8-5-1 in 1964, their fourth season, and outwardly there was a promising future for Norm Van Brocklin and Fran Tarkenton. Except, behind the scenes, the coach and the quarterback detested one another, the team went backward, Tarkenton demanded a trade and Van Brocklin resigned after the 1966 season.

Bud Grant came in from his big success as coach of the Winnipeg Blue Bombers. A season earlier, Notre Dame coach Ara Parseghian had settled famously for a tie in a titanic game with Michigan State, and “Tie One for Ara’’ became a sarcastic one-liner in college football.

Grant went 3-8-3 in his first year, and “Tie One for Bud’’ became the humorous mantra for the 1967 season among Minnesotans.

Meantime, General Manager Jim Finks brought in tremendous young talent through the trade of Tarkenton to the New York Giants (and also Tommy Mason to the L.A. Rams).

Green Bay won the first two Super Bowls, but Vince Lombardi saw his team getting old and quit as the coach. The Packers and St. Vince were 11-3 against the Vikings at that point.

It hardly had been a rivalry, and then the power turned on Sept. 22, 1968 in Lambeau Field. The young Vikings put a 26-13 thumping on the Packers. Joe Kapp was efficient at quarterback, Bill Brown carried the load on the ground, and the then-untitled Purple People Eaters devoured the Packers offense and Bart Starr.

The Vikings swept the Packers for the first time, finished 8-6 to win the NFL Central, made a first playoff appearance (a loss at Baltimore) and then became the No. 1 force in both the Central and the conference.

Over the next nine seasons, the Vikings won nine playoff games and played in four Super Bowls. Starting in 1968, the Packers appeared in one playoff game in 14 seasons.

Yes, those were the days when God-fearing, true Minnesotans didn’t have to take any guff from the Milton Waddams-types from Wisconsin, working in the same “Office Space.’’

BEHIND THE EIGHT BALL (1978): Tarkenton came back to the Vikings in 1972, became a record-setter and won three NFC championships, but he turned 38 in February 1978 and was coming off a broken leg suffered the previous November.

If this had been the modern, more-ruthless NFL, the Vikings would’ve sent Tarkenton packing and turned the team over to young Tommy Kramer. Instead, Grant gave Tarkenton a final season, Sir Francis threw 32 interceptions and also publicly blasted booing fans in the local newspapers.

Grant had no such tolerance for another noble veteran. He was upset that defensive tackle Alan Page, the greatest Viking ever, had decided unilaterally to trim down to 230 or so for health reasons. On Oct. 10, Grant had the Vikings cut Page, who wound up in Chicago on a $100 waiver claim.

I saw Bud and Alan run into one another on a summer day in Mankato a few years later, and the temperature dropped from 90 degrees to subfreezing when they shook hands.

That was also the end of the Vikings’ glory period, as they played in one losing playoff game over the next eight seasons.

THE HATEFUL EIGHT (1988): The actual Vikings were 8-4 in 1987, but they lost three scab games in that strike season, and had to back into the playoffs. Then, Anthony Carter played the most-brilliant playoff football this franchise has ever seen, and the Vikings had blowout wins at New Orleans and at San Franciso before losing in the dying moments of the NFC title game at Washington.

Expectations were through the Metrodome roof for 1988. The Vikings went 11-5, finished a game behind the Bears in the Central, and went to San Francisco for a first-round playoff game. Rather than repeating the Candlestick Park blowout of the previous season, the Vikings were embarrassed 34-9.

My recollection: I was walking behind a set of goalposts, toward the locker rooms, and someone shouted, “Hey, Reusse.’’ It was St. Paul Mayor George Latimer, and when I turned, he simply took his right thumb and index finger and squeezed his nose in an emphatic “they-stink’’ gesture.

The disappointment hung with Vikings boss Mike Lynn to such a degree that he made the Herschel Walker trade in October 1989. And that’s all that needs to be said about that.

THE CRAZY EIGHT (1998): Dennis Green spent seven seasons building a team and surviving controversies to get here: Jan. 17, 1999, the NFC Championship Game, with the 15-1 Vikings as 11-point favorites — enormous, when you consider Atlanta came to the Metrodome at 14-2.

Randy Moss had arrived to light the fuse on an explosive offense. All seats were filled again for games in the home dome, and it has stayed that way for the Vikings for 20 years.

It was the most-remarkable season in Vikings history and created a new, lasting generation of zealots. And also, for a kick in the stomach that ranks No. 1 with the Purple Faithful — rivaled only by the upset loss to Kansas City in the first Super Bowl appearance (January 1970).

It was a fabulous football game, and the Falcons handled the Dome madness tremendously, and yet the Vikings’ 30-27 loss in overtime … well, I still have Brian Peterson’s photo of the “Weeping Blondes’’ attached to the back of a door in the home garage. See those sad ladies twice a day (minimum).

THE HARD EIGHT (2008): Coach Brad Childress was on probation with the public for his predictable offense and odd style of communication, but by his third season, he had jacked up the post-Moss roster and earned a playoff spot with a dramatic rally vs. the New York Giants in the regular-season finale at the Metrodome.

Down 19-10 in the fourth quarter, Tarvaris Jackson threw a 54-yard touchdown to Bernard Berrian (see, Bernie wasn’t all bad) and then Ryan Longwell kicked a 51-yard field goal as time expired.

A week later, Tarvaris threw that awful pick-six to Philadelphia’s Asante Samuel, leading to a 26-14 playoff loss, and the Vikings went and got Brett Favre for 2009, and that sure was fun, wasn’t it?

And now:

THE SUPER EIGHT (2018): Oh, yeah. It’s happening. This is a team with more overall talent and much-greater depth than the 1998 — and a with better quarterback now in 30-year-old Kirk Cousins than they had then in 35-year-old Randall Cunningham.

This is it. The Vikings are going to win it all, because this team is loaded, and also when it happens, it’s going to be in a Season of Eight.