This is the most important week of the NFL season. Here’s why.

Of the 16 games, 12 feature at least one team that holds a playoff spot or is within a game of one.

New England Patriots wide receiver Julian Edelman (11) runs the ball, during the first half of an NFL football game against the Miami Dolphins, Sunday, Dec. 9, 2018, in Miami Gardens, Fla. (
New England Patriots wide receiver Julian Edelman runs the ball, during the first half of an NFL football game against the Miami Dolphins, Sunday, Dec. 9, 2018, in Miami Gardens, Fla. –AP Photo/Lynne Sladky

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An NFL game played in December counts the same as a game played in September — and yet, it doesn’t. The later it gets, every play grows fraught with consequence in a way it didn’t, it couldn’t, before the season’s final thrust.

Week 15 abounds with pivotal clashes, and the results will both tidy the playoff picture and muddle it deeper. Of the 16 games, 12 feature at least one team that holds a playoff spot or is within a game of one. Distilled further: Six of those matchups are between contending teams.

The games that most figure to influence the playoff field will be contested in Pittsburgh, Minneapolis, Indianapolis and Kansas City, where this critical week begins Thursday night, with first place in the AFC West — and potentially more — at stake for the Chiefs and the Chargers.

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With assistance from The New York Times’ Playoff Simulator, here’s a look at how those games will shape each of the involved teams’ postseason chances.

New England Patriots (9-4) at Pittsburgh Steelers (7-5-1)

Sunday, 4:25 p.m., on CBS

Three weeks ago, the Pittsburgh Steelers had the second-best record in the AFC.

Three straight losses later, the Steelers face the prospect of not winning their own division, and potentially not even advancing to the postseason should they lose to New England.

Unfathomable as that may seem, Pittsburgh’s playoff odds, currently at 68 percent, would crash to 48 percent with a loss, and its division title odds would fall to 45 percent. Defeating the Patriots would pump up the Steelers’ playoff chances to 87 percent and their division chances to 78 percent, fending off the Baltimore Ravens for at least another week.

The Patriots’ concerns are equally dire because, face it, they probably won’t earn home-field advantage in the AFC playoffs. That’s a huge deal in New England, which has hosted the conference championship game in five of the past seven years.

The Patriots have neither clinched a playoff berth nor their 97th consecutive AFC East title (or is it their 98th?). As it stands now, though, they have a 67 percent chance of earning their ninth consecutive first-round bye but only a 6 percent chance of the No. 1 seed. Should they shove Pittsburgh deeper into the abyss, the Patriots get a bye in 88 percent of the scenarios and the top seed 15 percent of the time.

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For all of New England’s dominance in recent years, the Patriots don’t make the Super Bowl when they lack home-field advantage in the playoffs. Their last three road playoff losses have come in the conference championship: 2014 and 2016 at Denver, and 2007 at Indianapolis.

A loss in Pittsburgh wouldn’t necessarily relegate New England to playing on wild-card weekend — the Patriots would still have a 52 percent chance of earning a bye — but it would surely heighten the drama quotient heading into the final two weeks.

When they host Buffalo and the New York Jets.

Oh, well.

Dallas Cowboys (8-5) at Indianapolis Colts (7-6)

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Sunday, 1 p.m., Fox

The longest winning streak in the NFL belongs to the team lampooned for trading a first-round pick for receiver Amari Cooper. But with 35 receptions for 584 yards and five touchdowns in his past five games, Cooper has helped propel the Cowboys to five consecutive victories. Without him, Dallas most likely would be meandering on the periphery of the playoff race instead of entrenched in first place in the NFC East, a division title all but guaranteed.

A win at Indianapolis would clinch that title for the Cowboys, who probably won’t catch New Orleans or Los Angeles for a first-round bye. They could still overtake Chicago, the expected NFC North champion, for the No. 3 seed, but it is far more plausible that the Cowboys finish fourth in the conference — a 76 percent chance, at present, that drops to only 70 percent if Dallas beats the Colts.

Considering the logjam of 7-6 teams led by Baltimore, it’s hard to envision Indianapolis sneaking into the playoffs if it loses Sunday. Then again, it was hard to envision Indianapolis winning at Houston, which had won nine in a row, after the Colts had been shut out by Jacksonville a week earlier.

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The Colts have a 31 percent chance of making the postseason and those odds plunge to 20 with a loss Sunday. Defeating Dallas would also maintain the Colts’ slimmer-than-a-microphone-stand hopes — 9 percent — of capturing the AFC South, regardless of how division-leading Houston fares against the Jets on Saturday.

Los Angeles Chargers (10-3) at Kansas City Chiefs (11-2)

Thursday, 8:20 p.m., on Fox

And now, for Patrick Mahomes’ next trick. After a masterful escape against the Ravens on Sunday, Mahomes can seal the AFC West title and a first-round bye for Kansas City — and all but lock up the No. 1 seed — with a victory Thursday night at home against the Chargers.

With their two-game lead over New England and Houston, the Chiefs would have a 97 percent chance of snaring home-field advantage throughout the playoffs by overcoming Los Angeles. A loss creates some suspense across the final two weeks, diminishing the Chiefs’ probabilities of securing a bye in the playoffs to 75 percent and the top seed to 64 percent.

Any other year the Chargers would be poised to win the division and host a playoff game. Just their luck that their best team since 2009 happens to coalesce the same year that a division rival fields one of the most electrifying offenses in league history.

Imagine the Chargers finishing with the second-best record in the conference but entering the playoffs as only the No. 5 seed. It’s quite possible; they are the AFC’s first wild-card team in 87 percent of the scenarios.

A loss Sunday has no effect on the Chargers’ playoff chances. But if they beat Kansas City for the first time since 2013, their odds of winning the division swell to 26 percent from 11. Though the teams would be tied atop the AFC West, Kansas City would hold the tiebreaker because of its better record in divisional games.

Miami Dolphins (7-6) at Minnesota Vikings (6-6-1)

Sunday, 1 p.m., CBS

All that separates the Dolphins — a team that lost four of five earlier this season, features one of the NFL’s more feeble passing offenses, and has a defense that ranks among the league’s worst in stopping the run, the pass and teams on third down — from the No. 6 seed, at present, is one fewer victory than Baltimore against common opponents.

Yeah, we’re dumbfounded, too.

The chances of the Dolphins emerging as a playoff team from this morass are pegged at about 20 percent. Those chances increase to about 38 percent with a win at Minnesota and plunge to 12 percent with a loss.

Which, it should be noted, is still better than the 0.1 percent probability they had of beating New England on Sunday, trailing by five with the ball at their 31-yard line and seven seconds remaining. If the Dolphins’ laterals galore could generate a 69-yard game-winning touchdown as time expired, then they can certainly win at Minnesota.

The Vikings’ inadequacies were on full display in a 21-7 loss Monday night at Seattle. They fired their offensive coordinator, John DeFilippo, on Tuesday. The Seahawks (8-5) have a 98 percent chance of capturing a playoff spot, which, since the Rams already clinched the NFC West, would be a wild card. The other wild-card spot, remarkably enough, still has a decent chance of going to Minnesota, which makes the playoffs in 51 percent of scenarios.

The mediocrity (or worse) in the NFC — hello, Panthers, Eagles, Packers and Falcons — has by default elevated the Vikings to contender. From their perspective, Sunday’s matchup with Miami is one of the bigger swing games of the week. A victory over the Dolphins inflates Minnesota’s odds of making the playoffs to about 68 percent, while a loss drops them to about 22 percent.