The Houston Texans and Baltimore Ravens, meanwhile, picked the wrong time of year to suffer the statistical chills. These two teams need a dramatic change of fortunes to return to the contender status they enjoyed at various times earlier in the season.
Newtonian physics tells us that the greater the momentum of an object, the greater the force it takes to stop it. Put another way, it takes a lot more effort to beat a red-hot football team.
The laws of football physics are not quite as exact as the laws of nature, of course. After all, teams are something more complex and organic than an inanimate object hurling through space. The various motivations and foibles of flawed humans, not to mention the odd and seemingly random bounces of an oblate spheroid, can impact outcomes in ways that the laws of nature cannot easily predict.
But it's still an interesting if inexact exercise to gauge momentum in the NFL -- who's hot and who's not entering the playoffs -- and then determine if it even matters.
The 2012 postseason provides a perfect case study in momentum: an interesting mix of teams, some great and some mediocre, that are either peaking at the right time or falling apart at the wrong time. Each of the 12 playoff contenders has a fairly distinct statistical storyline that tells us who's hot and who's not entering the postseason.
There are many methods we can use to test momentum entering the playoffs. The most obvious, of course, and the most important, is wins and losses: the hands-down winner in that case, of course, is Denver. Peyton Manning's mile-high crew powers into the postseason with 11 straight victories.
The method we prefer to use to gauge a team's statistical momentum is Passer Rating Differential -- that's the difference between your Offensive Passer Rating and your Defensive Passer Rating (the formula for quarterbacks applied to pass defense).
Passer Rating and Defensive Passer Rating alone are fairly telling indicators of team success. Highly efficient quarterbacks win a lot of games. Defenses that make opponents highly inefficient win a lot of games, too.
Subtract one from the other and you have Passer Rating Differential, or what we call the Mother of All Stats because it's so deadly accurate at separating winners from losers and champs from chumps, and has been through all of NFL history.
You win more than 80 percent of all NFL games when your quarterback posts a higher passer rating than the opposing quarterback. In fact, teams that won the battle of Passer Rating Differential in 2012 went 209-46 (.820). For the sake of comparison, teams that passed for more yards went just 127-125 (.504).
More importantly, you win championships when you dominate Passer Rating Differential: 36 percent of all NFL champions since 1940 finished the year No. 1 in Passer Rating Differential.
That's pretty amazing: if you looked only at Passer Rating Differential and nothing else, you could pick the champion out of a lineup of all NFL teams in better than 1 in 3 seasons since 1940.
More than 60 percent of NFL champions finished in the top 3 in PRD. That's good news for this year's top three: Green Bay (+31.5), Seattle (+28.8) and Denver (+25.9).
Here's a look at the relative statistical heat of each Super Bowl contender entering the postseason.
Atlanta bottomed out heading into the Tampa game in Week 12, after narrowly edging out the struggling Cardinals in Week 11. Matt Ryan and the gang have regained some momentum here at the end of the season (+22.0), but they are still playing far below their lofty early season standards entering the postseason. The Falcons need to pick up the pace.
The Ravens peaked early, very early, with their Week 1 44-13 win over the Bengals -- the victory that caused everyone, if only for a moment, to name Joe Flacco the NFL's elite young QB du jour. Baltimore hit rock bottom mid-season (+2.64 PRD) and has barely regained momentum entering its wild-card game (+5.78) -- not a good sign as they prepare to host the surging Colts.
Cincinnati has gone 7-1 over the second half of the season and has been consistently good, but not great in PRD, since Week 13. They're a team that's still only slightly above average -- but playing as well as they have all year, closing out the season just 0.6 points shy of its season high in PRD.
Since midseason, the Broncos have steamed forward as steadily and unstoppably as any team in football, consistently around +25 in Passer Rating Differential and peaking at just the right time with their highest number of the year entering the playoffs. Denver is very strong on both offense and defense and, right now, playing its best ball of the season. It's a scary good combination.
Green Bay (11-5)
The Packers stumbled out of the gate with their 30-22 loss to the 49ers">49ers in Week 1, a game in which San Francisco dominated the passer rating battle (+32.4). The Pack quickly recovered and, since beating up Houston in Week 6, has consistently led the NFL in PRD.
They are dominant in this number, but not necessarily hot.
Green Bay proves the power of Passer Rating Differential through years, that you win when you dominate through the air. Just ask Vince Lombardi's Packers. They finished No. 1 in PRD in 1961, 1962, 1965 and 1966 and won NFL titles each year. They were No. 3 in 1967, before turning it on in the playoffs (+42.5 PRD in three games) and winning yet another NFL title and Super Bowl.
Houston statistically bottomed out entering Week 7, after the crushing 42-24 home loss to Green Bay that exposed all the flaws in what appeared to be a Super Bowl contender. It the Texans were the Titanic, the Green Bay game was the moment they hit the iceberg.
Houston has taken on statistical water since that game and enters the playoffs just a point above their season low in Passer Rating Differential.
Indy has been negative in PRD all season and still is today. Andrew Luck has put up big volume numbers, but has been largely inefficient thanks to a low completion percentage and high number of turnovers (remember, even Peyton Manning threw 28 picks as a rookie).
The season started ugly, too, with a 41-21 loss to the Bears. But the Colts have displayed plenty of moxie over the course of the season: slowly getting better each and every week. Indy has never been better than it is today -- but that's still only lukewarm at best. The postseason won't last long. But the future looks very bright.
Adrian Peterson is fresh off one of the best seasons by a running back in NFL history, with 2,097 rushing yards and a Jim Brown-esque 6.0 YPA. But the reality is that running backs, even the greatest, never carry teams to championships alone. They need the help of a strong passing game. And the Vikings don't have one.
In the passing game, where it matters most, the Vikings are deficient on both sides of the ball. They join the Colts as the only playoff teams under water in Passer Rating Differential. Only two teams since 1940 have been negative in PRD and won a championship: the 1957 Lions (-4.5) and 2007 Giants (-10.4). The Vikings are fighting against the weight of history, even with Peterson.
New England (12-4)
Tom Brady's Bunch pulled it back together with a 9-1 record in their final 10 and has largely been on the upswing, gaining momentum here when it matters most late in the year.
But it's been decidedly imbalanced: the No. 3 scoring offense in history (557 points) was powered by an elite passing attack, but the team as a whole was weighed down by a merely average defense (No. 17 in Defensive Passer Rating).
New England is hot enough to win it all and has a passing game good enough to win it all. But the Patriots could easily short-circuit as the most imbalanced team in the playoff field.
San Francisco (11-4-1)
The 49ers won 11 games, enjoy a first-round bye and they are a threat to beat anybody. Yet they've failed to win more than two games in a row this year: big wins over teams like Green Bay, Seattle and Chicago were punctuated by bad losses to the Giants and Seahawks, and by a 0-1-1 record in two overtime games against the second-rate Rams (7-8-1).
Jim Harbaugh's bold move to bench Alex Smith and start untested Colin Kaepernick has not yet paid off, at least if you value the power of Passer Rating Differential: Kaepernick's rating is 6 points lower than Smith's. The 49ers ranked No. 2 in PRD (+29.0) with Smith still the starter. They end the season No. 4 (+23.2).
Bottom line: Kaepernick has not yet paid off in any meaningful statistical way.
Seattle's Passer Rating Differential chart shows the greatest upward trajectory of any 2012 playoff contender.
The Seahawks literally started with their worst game of the season, a 20-16 loss to the Cardinals that now seems hard to comprehend in retrospect given the condition of each team at the end of the year. They slowly got their feet under them with a controversial win over Green Bay in Week 3 and a narrow win over the dynastic Patriots in Week 6.
It's all rolled their way since then, punctuated by five straight wins to end the season, including an incredible 150 points scored in Weeks 14, 15 and 16. Seattle is hugely balanced on both sides of the ball: rookie Russell Wilson has powered a unit that is No. 5 in Offensive Passer Rating (100.6) and it's paired with a unit that's No. 3 in Defensive Passer Rating (71.8), the best pass defense of any playoff team.
The Redskins had nowhere to go but down after that game -- but they have steadily picked up down the stretch, as evidenced by their seven-game win streak and No. 6 ranking in PRD.
But, like the Patriots, the red-hot Redskins do suffer from imbalance: Thanks to RGIII's incredible rookie season, Washington is No. 3 in Offensive Passer Rating (and No. 1 in Real QB Rating). But it is only a second-rate team on the other side of the ball: No. 18 in Defensive Passer Rating.
The Redskins have won largely in spite of their defense -- and will have to do so again to make noise in the playoffs. With that said, the team is largely playing its best ball since its Week 1 explosion here down the stretch.