The NFL's final four doesn't include any mistakes. You have the league's most explosive passing attack (Arizona) and the league's most efficient passing game (New England). There is the NFL's most dominant running game (Carolina), and while the Denver Broncos haven't had much of an offense this season, they feature the league's top defense by just about every advanced metric. These are teams that excel at an extremely high level, that force you to adapt and make it extremely difficult to counter or shift strategies midgame.
So, how do you beat them? There are the obvious scenarios that slay all teams; you can get a game in which your defense recovers three fumbles and forces a couple of picks, or one in which the opposing quarterback gets injured in the first quarter. You can beat the Cardinals easily if Carson Palmer has his worst game of the season, like he did against Seattle in Week 17. Those scenarios work, but they're hardly interesting or predicative.
And these teams each lost at least once in December -- three of them over the final two weeks -- which should again push away the idea that teams that get hot before the playoffs stay hot into January. The Patriots team that lost its final two games of the regular season isn't the same team that comfortably handled the Chiefs on Saturday. The teams we saw then aren't necessarily the teams that will line up to play in the Super Bowl.
Each of these teams has weaknesses which other teams have exploited during the season in various ways. Sometimes, those issues have been minor nuisances; in other cases, they have cost these teams games.
Given that these four organizations are playing so well, there just aren't many ways to actually take them down or give them fits. If you do, here's how it might happen.
New England Patriots (12-4)
Blueprint: Get the pass rush after Tom Brady.
Slowing down Brady by winning up front and getting pressure (preferably up the middle) has been the classic trope for how to beat the Patriots in the playoffs. It's how the Giants pulled off their upset of Brady and the undefeated Patriots in Super Bowl XLII, how the Jets and Mark Sanchez upset the Pats in Foxborough, Massachusetts, during the 2010 postseason, and how the Seahawks got out to their early lead in last year's Super Bowl. Michael Bennett spent most of the first three quarters terrorizing Brady, but once the Seahawks lost Cliff Avril and Bennett subsequently slowed down, Brady kicked it into high gear and won his fourth ring (yes, with a little help).
The same thing is true of this 2015 Patriots team, and the absence of the Kansas City rush was a big reason why the Patriots had so much success on offense on Saturday afternoon. With Justin Houston (29.5 sacks in 27 regular-season games over the past two years) playing just eight defensive snaps, the Chiefs were forced to blitz to try to generate pressure. That was no trouble for the Patriots, who picked up first downs on consecutive third-and-longs to start the game against Kansas City blitzes, subsequently scored a touchdown, and never looked back. The Chiefs eventually finished the game with no sacks, pressured Brady on just four of 43 dropbacks, and registered just one legal quarterback hit, from Houston replacement Dee Ford. They didn't even get a sniff of Brady.
Compare that to the final two games of the regular season, when Brady was knocked down a combined 13 times by the Dolphins and Jets in losses. The Patriots don't turn to mush when Brady's under pressure, but it does slow them significantly. Of the five games in which Brady was pressured most frequently this season, the Patriots lost three, including their 30-24 setback against the Broncos in Week 12. The two games they won were against the Bills (in their second meeting) and the Giants, which they won by a combined eight points. And all of these games came during the second half of the season, as New England's line struggled because of injuries.
The Broncos can get pressure on Brady, of course; a team that has Von Miller and DeMarcus Ware is always going to be capable of getting at least some form of pressure. The problem is that the rush has established a nasty habit of going missing during Denver's crushing playoff losses. That was true in the 2013 season, when the Broncos failed to sack Russell Wilson once during their blowout loss in the Super Bowl. And it was true again the following year, when the Broncos failed to take down the eminently sackable Andrew Luck during their home loss to the Colts.
This has been Denver's crucible in 2015, too. Three of the Broncos' four losses have come in the four games in which they posted their lowest pressure rates on defense, per ESPN Stats & Information. The one exception there was a 24-12 win over the Lions during which the Broncos got two short fields in the fourth quarter off turnovers to barely pull away. If one issue can decide the AFC Championship Game, it very well may be whether the Denver pass rush shows up when the Broncos need it most.
Denver Broncos (12-4)
Blueprint: Slow down the running game.
With the Denver passing attack in shambles under Gary Kubiak this season, much of the Broncos' offensive output has come from their ground game. The numbers don't look great for the rushing attack because teams are crowding the line of scrimmage, especially with Peyton Manning around, but the effectiveness of the Broncos' running game is a key to their success.
Stats noting how effective an offense is when its running back rushes for 150 yards or more are often nonsensical results of cause and effect; often, they're noting how a team got ahead early and pounded the ball with its starter to chew up clock in the second half, not how effective it actually was at running the football. Offenses like those of the Patriots, Chiefs and Seahawks all played much better this weekend as they abandoned the run altogether and threw on virtually every down.
However, we can use an advanced metric to see just how meaningful the Broncos' running game can be. The same win probability framework that influences QBR can be used to analyze a team's performance in other categories of the game, and that includes its performance when running the ball. There, the link between Denver's rushing attack and its success is crystallized.
When the Broncos this season have added win probability in some way by running the football -- when their running game simply adds to the mix -- they're 7-0. When the running game takes something off the table, whether it be by inefficiency, fumbles or other poor play, Denver is a far more pedestrian 6-4, including its narrow win over the Steelers on Sunday evening.
The same split is even more heavily defined for the Patriots. It's simple: When opposing teams add any win probability with their running game this season, the Pats are 0-4. When the opposing running game has cost itself even 0.01 of a point of win expectancy or more, the Patriots are 13-0.
Carolina Panthers (15-1)
Blueprint: Get out of the pocket.
There's not much you can do to beat the Carolina pass defense. It's not easy when the Panthers' front four reduces your offensive line to ash and forces your quarterback to throw two ugly interceptions, as Carolina did to Russell Wilson during the first half of Sunday's home victory. The Panthers don't necessarily need to beat up the opposing offense to win; they posted the league's third-best QBR across all situations this season, but they were still the ninth-ranked defense in the league by QBR when they failed to get pressure on the opposing passer. They just cover too much ground. Consider the play Luke Kuechly made in the second half on Sunday, when he managed to fan out and knock away a corner route 20 yards downfield. Normal linebackers just don't do that.
The Panthers are too athletic and too well-coached to beat on a regular basis. The one way you can really stretch them, though, is to get them out of their comfort zone and force them to improvise. You do that by getting out of the pocket. When the Panthers kept opposing passers in the pocket this season, they were dominant, posting a league-best opposing QBR of 38.2. Outside the pocket? Not so good. Their QBR nearly doubled, going up to 71.1. The league's best unit inside the pocket fell all the way to 27th once passers got outside.
Here's the disconcerting thing if you're a Cardinals fan, though: The Cardinals posted the league's best QBR on offense this season, and they were the third-best passing attack in the league when Palmer made his way outside the pocket, but he rarely made it out there. The Cards threw just 38 passes from outside the pocket all season. That was 6.9 percent of their pass attempts in 2015, the fourth-lowest rate in football. Only the Steelers, Patriots and Chargers got outside less frequently. In a possibly related note, the starting quarterbacks for three of those four teams have undergone ACL surgery during their professional careers (Ben Roethlisberger is the exception, and he suffered an MCL sprain earlier this season). It doesn't seem like an easy fix for the Cardinals, given how they play, but it's the right way to go after Carolina.
Arizona Cardinals (13-3)
Blueprint: Force them to run in short-yardage situations.
The Cardinals don't have many weaknesses on offense under Bruce Arians. They can chuck the ball downfield, generate big plays with their running game, and pick up third-and-a-mile like it's nothing. When they're clicking, the Cardinals are a breathtaking offense to watch.
The one area in which they do seem to struggle, though, is running the ball for short yardage. It has been a major problem for the Cards this season. Football Outsiders tracks a stat called power efficiency, which is how a team does running the football in common short-yardage situations. They include runs on third and fourth down with 2 yards or less to go, as well as all runs within 2 yards of the end zone, regardless of down.
The Cardinals are an effective running game in most situations, in part because defenses are terrified of John Brown and Larry Fitzgerald beating them deep. So they position their safeties somewhere near the tunnel. In short-yardage situations, that isn't the case. The Cards have converted just 51 percent of their power runs this season when the league average is a robust 65 percent. That's the fourth-worst rate in football, and it's a stark contrast to the Cam Newton-led Panthers. Carolina's offense picks up 76 percent of power situations, the second-best rate in football.
The Arizona offense isn't facing Newton, though; it's facing the Carolina defense. And while the Panthers' defense is wildly effective at just about everything, the one thing it bizarrely can't seem to stop, of all things, is opposing teams in short-yardage situations. The Panthers are somehow allowing opposing offenses to convert 87 percent of their runs in power situations for first downs or touchdowns. That's the worst rate in football. Just odd.
Opposing offenses are 20-for-23 on those runs against Carolina, with the three stops coming against the lowly rushing attacks of the Colts and Titans. The Panthers certainly have the talent up front to come up with short-yardage stops, but it hasn't been happening for them this season. If the game comes down to the Cardinals in a power situation, it will be the rare matchup in which both of these teams -- two of the league's best -- simply haven't been very competent this season.