Passer rating differential is the most reliable indicator of championship potential in all of North American sports. It’s the mother of all stats.

And the picture she paints for the Patriots is a hazy, confusing splotch of pigskin impressionism. With a full complement of weapons early in the season, the Pats were one of the NFL’s dominant statistical powers. The trend since then has been sharply downward, a spiral that began not with the 2-4 record since Thanksgiving but as early as Week 6.

The Patriots reached their statistical peak following their 30-6 rout of Dallas in Week 5. They emerged from that game plus-37.8 in PRD, yet they enter the playoffs a mere plus-14.9, their lowest mark of the entire campaign. Put another way, they enter the postseason as statistically suspect as they’ve looked all year.

But here’s the good news for Patriots fans: The team still is ranked No. 6 in the NFL in PRD. And that offers plenty of statistical confidence.

Passer rating differential simply measures the disparity between offensive passer rating and defensive passer rating (or the efficiency of all opposing quarterbacks against a team’s defense).

The importance of this indicator throughout NFL history cannot be understated, as 27-of-75 league champs (36 percent) since 1940 finished No. 1 in PRD, 45 (60 percent) ranked in the top three and 71 (94.7 percent) were in the top 10.

Week in and week out, year after year, decade after decade, the teams that dominate the battle of passing efficiency dominate on the scoreboard and in the standings. The 2015 season was no exception: The teams that produced the top 103 performances in PRD were an incredible 100-3.

The Patriots were 9-1 when they won the battle of passing efficiency. Their 2-4 stumble at the finish line coincided with — indeed was caused by — an inability to consistently win the battle of pass efficiency. But hope is not lost.

The AFC playoff field is, statistically speaking, among the weakest in history, with three flawed contenders (Broncos, Steelers, Texans) and two that look statistically stout but have poor postseason histories and huge question marks at quarterback (Bengals, Chiefs). None possesses the historic statistical profile of an NFL champion.

Here’s a look at the PRD profile of each AFC contender, plus a quick look at the field of NFC contenders, with a special focus on how each team has trended in the mother of all stats.

Cincinnati: The Bengals were the most consistent statistical force in the AFC. They started strong with a plus-30.2 PRD in their dominant Week 1 win against Oakland and rarely wavered. They enter the playoffs plus-25.2, best in the AFC. But Cincy has huge questions at QB: Injured starter Andy Dalton is 0-4 in his postseason career with a dismal 57.8 passer rating. Backup A.J. McCarron has started just three NFL games.

Kansas City: The Chiefs are the hottest team in the AFC, both on the scoreboard. They’ve won 10 straight and have trended upward in PRD every week of the streak. Their plus-19.4 PRD is No. 2 in the AFC. The Chiefs pair the second-best pass defense in football (76.0 defensive passer rating) with hugely efficient QB Alex Smith. But Smith has limited playoff experience: He’s 1-2 in 10 NFL seasons.

Denver: The Broncos are a statistical anomaly, going 12-4 with the AFC’s No. 1 seed despite habitually poor QB play and a PRD of minus-2.5. Only two teams in NFL history were upside-down in PRD and won a championship: the 1957 Lions and the 2007 Giants, who upset the unbeaten Patriots.

Denver statistically peaked in Week 2 (plus-29.2 PRD) while Peyton Manning threw 17 interceptions in just 10 games. And his playoff record is spottier than a Dalmatian with measles. Manning’s normally high-powered teams have averaged a dismal 15.2 points in his 13 career playoff losses. Don’t count on him to deliver this year, either.

Pittsburgh: The Steelers were consistently mediocre in 2015 and enter the postseason plus-0.30 in PRD, 16th in the NFL. Only one team in history won a championship with a PRD ranking worse than 12th: the 2007 Giants (24th).

Ben Roethlisberger put up big numbers but threw 16 picks in just 12 games, and he’s paired with a mediocre pass defense. It’s a bad combo. Pittsburgh’s six Super Bowl champs all were dominant in PRD. This team is not.

Houston: The Texans enter the playoffs plus-2.5 in PRD, their best mark of the season. Houston pairs a slightly above-average pass defense with a below-average passing game led by unproven Brian Hoyer (26 career starts). That combination spells an early playoff exit.

The NFC field: The Seahawks surged through the second half of the season behind an increasingly tough defense and the league’s most efficient QB in Russell Wilson (110.1 passer rating). They topped the NFL in PRD for just the second time in franchise history. The first was in 2013 when, not coincidentally, they won the Super Bowl.

The 15-1 Panthers finished No. 2 in PRD, while the statistically powerful Cardinals topped the PRD leaderboard much of the season before finishing fourth.

Bottom line for the Pats: Despite the long period of statistical struggles and with a slew of injured players returning for the playoffs, they are no worse than a 50-50 proposition to win the AFC and return to the Super Bowl for a seventh time in the Tom Brady era.

But don’t count on the Patriots to win it all. NFC powers Seattle, Carolina and Arizona would be — and should be — favored to beat the Patriots in Super Bowl 50.

Kerry J. Byrne is the founder of ColdHardFootballFacts.com? and FootballNation.com.