Seattle’s Pete Carroll and Arizona’s Bruce Arians are nearly football-plan twins. / Drew McKenzie, Sportspress Northwest

About this time every year we are made aware of a loud noise  . . . “there arose such a clatter . . . ” 

When we all leap to see what was the matter, traditionally we are asked to imagine a jolly old elf. I bought it until this year, when I realized the din was the four NFC West teams beating the bejeezus out of one another.

The conclusion of the NFL regular season Sunday includes the final division collisions: The 12-3 Seahawks host the 7-8 St. Louis Rams and the 11-4 San Francisco 49ers visit the 10-5 Arizona Cardinals. The thrashes should generate clatter akin to dropping a mile of train tracks off the Space Needle.

Hide the chillruns.

“This division used to be the laughingstock of football,” said Seahawks safety Earl Thomas Wednesday. “Now everybody knows this is the best division. It’s a great competition. Every game is hard. Like the Big 12.”

The University of Texas homeboy is entitled to his bias. But if college football were played this harshly, university presidents would be in orange coveralls awaiting charges of student abuse. There is no dispute that, with a collective record of of 40-20, the NFC West is the gnarliest neighborhood in pro football.

“I’ve been in this division eight years,” said FB Michael Robinson. “It’s been the same: Tough defense and running the ball. Same style, different performance (this year).”

When the 7-9 Seahawks won the division title in Pete Carroll’s first year of 2009, the first losing team in NFL history so honored, the Seahawks and the division were mocked as serfs unfit to mop the castle floors.

“Yeah, it’s come a tremendous distance,” Carroll said last week. “(We had) to put up with the yuks about being 7-9 and winning the division years ago. Who’s laughing now?

“There’s also kind of an attitude about our division too — a very physical, tough kind of pride. It’s been kinda fun to watch it.”

If the Seahawks win Sunday, it is well understood that they are division champs and the NFC’s No. 1 seed, which earns the coveted home-field advantage as well as a first-round bye. It also would mean they finished divisional play at 4-2, which may be the highest form of merit badge on the brag rag.

But if Sunday the Seahawks lose and the Cardinals win over the Niners — evidence of the season makes both outcomes plausible — there will be a remarkable symmetry: San Francisco would finish 4-2 in the division, Seattle and Arizona would be 3-3 and St. Louis 2-4.

In that scenario, the Seahawks, at one point 11-1 and national darlings to win it all, would finish 12-4 having lost three of their final four games, all to division rivals.

Yeesh. That is prison-yard nasty.

However the weekend turns out, being king of this hill says something beyond the playoff advantages: Particularly in a football era of pass-happy, spread offenses, there is a place for the Eisenhower-ball that the four teams play.

“Everybody would like to talk about speeding up the game and spreading it out,” Carroll said. “There’s a lot of wins in this division. I guess you would say that it adds to the validity the formula that we go with.

“It’s no different for Arizona, San Francisco, and the Rams right now.”

The validation of style is, of course, far secondary to the Seahawks. In less than a week’s time, they have to figure a workaround for a Rams defense that is probably better than the Cardinals defense that Sunday held Seattle to 189 yards, 10 first downs and 10 points.

In the Oct. 28 first meeting in St. Louis, the Seahawks defense was nearly smothered on Monday Night Football — 135 yards and seven first downs. That they won 14-9 was due almost exclusively to one play — an 80-yard pass-and-run touchdown from Russell Wilson to Golden Tate.

Sunday is not a a get-well game for an ailing Seattle offense. It is merely another wet, cold stumble through an alley full of desperadoes, scoundrels and mace-wielding brigands. Or as NFC West fans call it, a beautiful day in the neighborhood.

Harvin done for the season?

The chance to see WR Percy Harvin play again this season grows dim. At each juncture lately, Carroll has grown increasingly circumspect in his assessment of whether the star wideout will return after his one appearance — 19 plays in the Nov. 17 game against Minnesota.

Asked Wednesday whether Harvin might be put on the injured reserve list, meaning he will not return until next season, Carroll said, “Yeah, that may happen.”

Harvin’s surgically repaired hip continues to bother him to the point where the Seahawks would prefer to fill his roster spot with a player who can help, rather than hope Harvin might be healthy for a playoff game or, football gods willing, the Super Bowl.

In the wake of the 17-10 loss to Arizona, Harvin’s absence loomed, because of what happened in Harvin’s areas of expertise — kickoff returns and getting separation downfield from defensive backs.

Robert Turbin fumbled away a kickoff return, and the Seahawks receivers could not shake the Cardinals’ coverage. It took 15 games, but the reason the Seahawks traded three draft picks and will pay $26.5 million in guaranteed salary  to get Harvin became apparent.