NFL teams are focused on this week’s opponents and how the playoff picture is shaping up

Reporting from CHICAGO —  As the calendar flips to December and the NFL heads into the final quarter of the regular season, lots of coaches are holding a play sheet in one hand and a calculator in the other.

The Rams are the only team to have clinched a playoff spot, but there’s much more at stake for them and incentive to keep winning. The rest of the league is on the verge of securing a berth, mathematically out of the running, or jostling somewhere in between and throwing elbows just to stay alive.

A couple of weeks ago, when the Rams beat the Kansas City Chiefs, 54-51, it seemed having a high-octane passing attack was the key to maintaining a strong pulse. But in the case of a lot of playoff-minded teams — namely, Seattle, Dallas, Baltimore, Denver and Tennessee — it’s all about the time-tested formula of a strong running game plus a smothering defense.

The Seahawks lead the league with a running game averaging 148.8 yards per game. Asked why he likes relying on the ground game so much, coach Pete Carroll had a simple answer.

“Because it’s the best way not to screw it up,” he told reporters this week. “It’s the best way to play the game, because the games are always lost. They’re always lost — you make errors. That’s why the turnover issue is of paramount importance to us.”

According to the Seattle Times, the Seahawks are 52-10 since 2010 when winning the turnover battle.

None of those five teams — Seahawks, Cowboys, Ravens, Broncos and Titans — is a lock for the postseason, and Denver and Tennessee would need some help, yet all are surging as they round the corner into the stretch run.

Kansas City (versus Baltimore), New England (at Miami), and New Orleans (at Tampa Bay) can secure playoff spots Sunday by winning. All are in solid position to grab one of the top two seeds in their respective conferences, thereby getting a week off when the postseason starts.

The Chiefs’ Patrick Mahomes needs just 77 yards passing to join Hall of Famers Dan Marino (1984) and Kurt Warner (1999) as the only first- or second-year quarterbacks to pass for at least 4,000 yards with 40 touchdowns in a season. Both Marino and Warner were named the league’s Most Valuable Player in those respective seasons, and Mahomes is well on his way toward earning that honor this season.

With a victory Sunday over the Buccaneers, the 10-2 Saints would clinch back-to-back division titles for the first time in their history.

“I think the most important thing is this team in front of us, this game in front of us, and finding a way to get to 11 – period,” said New Orleans coach Sean Payton, whose team also could secure the NFC South by Carolina losing to Cleveland. “They’re all smart enough to know that, hey, you’re chasing other things that could enhance your possible opportunities down the road, and so it’s that simple.”

At 9-3, the Chargers have the best record of any team not leading its division, and only the Rams, Saints and Chiefs have a better record.

Winning the AFC West isn’t out of the question for the Chargers, who play at Kansas City on Thursday, but that would entail a stumble by the Chiefs. The Chargers are the type of wild-card team no one wants to play, and because they aren’t reliant on a home-field advantage – StubHub is essentially a neutral field – they could be more battle-tested than most teams.

Sunday features a couple of intriguing matchups of elite offenses and defenses. It’s the Chiefs’ top-scoring offense (37.0 points per game) against the Ravens, who have the league’s stingiest defense (17.8). The Sunday night game pits the Rams, who have the No. 2 offense, against the Bears, whose defense is ranked third.

If the Rams were to win, they would not only be off to the best start in franchise history (12-1), but also would be guaranteed a first-round bye and keep the Saints at bay for the NFC’s No. 1 seed.

The Bears, meanwhile, are on track to maintain the NFL’s tradition of worst-to-first teams. In 14 of the past 15 seasons, at least one team finished in first place in its division the season after winding up in the cellar.

The Bears (NFC North) and Houston Texans (AFC South) are currently in first place in their respective divisions, with the Texans riding a league-best streak of nine wins in a row.

Meanwhile, Cleveland rookie Baker Mayfield has another nine-game streak going. He has thrown at least one touchdown pass in each of his first nine starts. If he were to get to 10 on Sunday against the Panthers, he would join Warner (1999) and Brad Johnson (1996-97) as the only quarterbacks to throw at least one touchdown pass in their first 10 career starts.

sam.farmer@latimes.com

Follow Sam Farmer on Twitter @LATimesfarmer