From Good to Not Great: The Cowboys, Raiders and why mediocrity reigns in the NFL

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It might seem like there's as much separation as ever between good and bad NFL teams. As I write this, Dallas and New England have a chance to go 14-2, while Cleveland could finish 0-16.

But as the NFL regular season draws to a close, a deeper look at the numbers reveals the opposite: Teams are bunched in talent much more closely than they appear. The league is at a crossroads, and the next few years will determine which contending franchises will rise to new dominance -- or whether that's even possible anymore.

The technical way to express how the gap between teams has shrunk is by standard deviation of team point differentials. That's down 16.3 percent this season (through Week 14) to its lowest point in at least five years -- which is to say that even the best teams aren't great and even the worst aren't historically awful. The Patriots, for instance, are on track to outscore opponents by 146 points, which would be the biggest margin in the NFL but the third smallest to lead the league in a 16-game schedule. Behind them, the Chiefs, Giants and Lions have won more than two-thirds of their games while beating their foes by fewer than 100 points combined. Meanwhile, the Browns, prorated, will be outscored by 207 points -- surely hideous, but not in the all-time bottom 40 since 1940 and nowhere close to the winless 2008 Lions (minus-249) or 1976 Buccaneers (minus-287).

It's mostly chance that teams look less squished together than they actually are. For one thing, the league's bottom-feeders have been pretty awful but also awfully unlucky. Through Week 14, Cleveland, San Francisco, Jacksonville and Chicago were a combined 3-19 in games decided by a touchdown or less. And at the other end of the standings, a handful of winning clubs have played severely over their heads. Dallas and Oakland might be popular favorites to meet in the Super Bowl, but both teams are on pace to outperform their underlying statistics by more than two wins this season. The Cowboys and Raiders are worthy contenders, but they're more similar to 10- or 11-win teams of the past than to 14- or 15-win juggernauts.

It's between these extremes that you can really see the NFL's compression: With two games remaining, 12 teams were on track to win eight to 10 games and were therefore at the lower end of playoff contention. That's a large group; only nine clubs posted eight to 10 wins in each of the past two seasons. And I think one reason for the big number is that many of these teams have lopsided rosters.

Consider Atlanta, tied atop the NFC South and gaining more yards per play and scoring more points than any other team in the NFL. The Falcons' offense is in fact 11.1 points per game above average after adjusting for opponents, according to Pro Football Reference's simple rating system, and their defense is 3.5 points per game below average. That difference is the largest since the 2013 Broncos, and that kind of disparity has become more common. Think of Houston, Indianapolis, Seattle ... Overall, eight teams have a gap of more than a TD per game between their offensive and defensive units this season -- twice as many as in any of the past three seasons.

So welcome to the season, and possibly the era, of the B-plus NFL team. As a handful of franchises bottom out and others, such as Carolina and Cincinnati, sag unexpectedly, there have been unanticipated wins to go around for the likes of Miami and Tampa Bay. But not one of the teams posting gains this season is great yet, and some are literally only half-good.

Any member of the burgeoning pretty-decent club might keep drafting well and evolve into, say, the next Steelers. But there's another possibility. From 2010 to 2015, the number of games that NFL teams' key players lost to injury jumped by 36 percent, according to Football Outsiders. Injuries might now be so rampant that it's practically impossible to build complete, high-quality units that survive intact for 16 weeks. After all, Green Bay didn't plan an unbalanced roster this year any more than Minnesota; injuries blew apart the Packers' defense and severely set back the Vikings' offense. It only takes one or two big names -- such as Clay Matthews or Teddy Bridgewater and Adrian Peterson -- to go down. As star athletes spend more time on the sideline, the standings are more likely to churn.

Lull or tipping point? We can't be sure yet what 2016 will prove to be. But we can already see the NFL is heading someplace different.