The most important stat in football

It's official, sports fans: Passer Rating Differential is the most important stat in football. It's the one indicator virtually guaranteed to separate winners

It's official, sports fans: Passer Rating Differential is the most important stat in football. It's the one indicator virtually guaranteed to separate winners from losers and champs from chumps.

If your team dominates this indicator, it dominates on the field. If your team's bad in this indicator, it's bad on the field.

Just ask the 2010 Super Bowl champion Packers, who finished the year No. 1 in Passer Rating Differential (+31.7), or the dismal 2010 Panthers, who finished the year with the league's worst record (2-14) and worst Passer Rating Differential (-24.0).

Put most simply, wins and losses move in lock step with Passer Rating Differential (PRD), a Cold, Hard Football Facts "Quality Stat" because it has a direct correlation to success. In this case, the correlation is shocking even to the folks who created the stat.

How good is the stat? Consider that 40 of 71 NFL champs since 1940 (56 percent) finished No. 1 or No. 2 in Passer Rating Differential.

We have long known that success in the NFL is all about highly efficient passing attacks -- and it always has been, dating to the dawn of the T-formation in the 1940s. The best offenses are those that pass the ball most effectively, as measured by passer rating. The best defenses are those that shut down opposing quarterbacks most effectively, as measured by what we call Defensive Passer Rating. The best teams are those that do both most effectively.

To prove the importance of passing efficiency, we introduced Passer Rating Differential before the 2009 season. It simply subtracts what we call a team's Defensive Passer Rating (the passer rating of a team's opponents) from its Offensive Passer Rating. It's been a runaway success, beyond even when we imagined.

New Orleans finished No. 1 in Passer Rating Differential in 2009, the first year of the indicator's existence. That year, the Saints won the Super Bowl. Green Bay finished No. 1 in Passer Rating Differential in 2010, and they, too, won the Super Bowl. That made us two for two picking Super Bowl winners simply by looking at the Passer Rating Differential charts.

But we needed to know more to prove this was no fluke. And, folks, it's no fluke.

During the 2010 postseason, we looked at the Passer Rating Differential of every single NFL champion since 1940, the year that saw the very beginnings of the modern quarterback position and modern passing game.

It was a treasure trove of data: the average NFL champion over the past 70 years produced a truly incredible Passer Rating Differential of +27.4 (82.3 Offensive Passer Rating vs. 54.9 Defensive Passer Rating). That's dominance in the passing game.

Our most recent round of analysis goes one step further than just looking at the champs. With a big assist from Cold, Hard Football Facts analyst, statistician and spreadsheet savant Luis DeLoureiro, we compiled the Passer Rating Differential of every team since 1940.

The findings give us an incredible cache of amazing data that we'll roll out throughout the 2011 season, all of it proving that Passer Rating Differential moves in lock step with wins and losses,

Below is a list of the Top 25 teams in Passer Rating Differential since 1960. We decided to go with 1960 because it's a watershed year in NFL history, with the advent of the AFL. But we also began at 1960 because many teams at the very top of the all-time Passer Rating Differential list, and almost every team at the bottom, were from the 1940s and 1950s.

The top three teams all time in PRD, for example, are the 1943 Bears (+73.3), 1941 Bears (+65.0) and 1942 Bears (+60.0). The worst teams all time in PRD all played in the 1940s, as well. At the bottom of the list is the 1945 Steelers (-70.2).

The disparity in PRD in the 1940s stood out as a clear statistical anomaly and spoke to many issues with football in that era: namely, a disparity in modernization -- some teams used the new T formation, Chicago most notably, and others didn't. There was also a disparity in talent, one that was aggravated by the roster depletions caused by World War II. The 1950s also produced a pretty noticeable disparity from top to bottom, though not as distinct as in the 1940s.

Here are some of our immediate reactions to this list:

The top 25 tells us that winning the Passer Rating Differential battle is the fast track to winning a championship in pro football: 14 of the Top 25 teams won NFL championships or Super Bowls. Three others lost in the championship game.

Of the 71 champions since 1940, an incredible 26 of them -- 37 percent -- finished No. 1 in Passer Rating Differential; another 14 finished No. 2 in Passer Rating Differential. In other words, 56 percent of NFL champions were No. 1 or No. 2 in PRD.

The top 25 teams were near impossible to beat, with a combined record of 299-63-4 (.822). The average team in the Top 25 won 12 games and lost 2.5 games.

Among the 11 teams in our Top 25 that failed to win a championship, three were stopped by other PRD juggernauts.

The 1960 Browns (No. 1 on the list) were edged out for the Eastern Conference championship, and an appearance in the NFL title game, by Norm Van Brocklin, Chuck Bednarik and the 1960 Eagles (No. 19 on the list). If not for a 31-29 loss to Philadelphia in October, the Browns, not the Eagles, would have battled Vince Lombardi's Packers in the 1960 NFL championship game.

Ken Anderson 's 1975 Bengals are No. 9 on the list. They went 11-1 that year against teams not from Pittsburgh, but lost both meetings with the Steelers (No. 6 on the list). Pittsburgh finished one game ahead of Cincinnati in the AFC Central and ended the year with its second consecutive Super Bowl victory.

The 1963 Giants (No. 10) and Bears (No. 13) met in the NFL title game, a 14-10 Chicago victory (more on that epic below).

Every great "dynasty" (1960s Packers, 1970s Steelers, 1980s/90s 49ers, 2000s Patriots) and near-dynasty (1970s Cowboys, 1970s Vikings, 1990s Rams) of the era is represented on the list, except for the largely overrated Cowboys of the 1990s -- a group that went better than 12-4 just once.

But one dynasty loomed larger than the rest.

Three teams in the top seven belonged to Bill Walsh. This cluster of San Francisco teams proves that the great genius Walsh, as Cold, Hard Football Facts have noted, was not that he popularized the West Coast offense. No, the great genius of Walsh was that he popularized the West Coast offense while creating arguably the greatest (and certainly most underappreciated) defensive dynasty in history.

For 17 straight years, the 49ers never surrendered more than 300 points in a season and they consistently produced very low Defensive Passer Ratings, usually among the very best in the NFL. We discussed this phenomenon a couple years ago and more recently this spring, as it related to Ken Anderson's Hall of Fame cred.

The fact that three of the top seven teams all come from the same organization in the same brief period of success is amazing.

Let's put it into statistical context: the 49ers won five titles not because they had Joe Montana and Steve Young. The 49ers won five titles because they had Montana and Young and consistently paired these great passers with the best pass defenses in football.

Two teams since 1960 have produced unbeaten regular seasons: the 1972 Dolphins and 2007 Patriots. Both are on this list.

Miami famously rolled to a Super Bowl title without a single blemish. The hard-choking Patriots were upended by the Giants in what is the greatest statistical upset in NFL championship play of at least the past 65 years.

After all, the Giants not only shocked the only 16-0 team in NFL history and the most prolific offense ever -- they did it with a team that simply had no business winning a championship. New York's Passer Rating Differential of -10.4 in 2007 is easily the worst of any champion in NFL history. In fact, the 2007 Giants are one of just two teams in history to win a championship with a negative Passer Rating Differential. The other was the 1957 Lions (-4.5).

You may have noticed Brett Favre's Super Bowl champion 1996 Packers are on the list. Even at the height of his powers in the mid-1990s, this greatest of all postseason liabilities needed to be paired with the NFL's No. 1 scoring defense to win a Super Bowl.

The 1996 Packers finished the year No. 1 in both Defensive Passer Rating and Passer Rating Differential. The Super Bowl champion 2010 Packers were also No. 1 in both Defensive Passer Rating and Passer Rating Differential.

The sad-sack Lions simply can do nothing right. Yes, we have high hopes for them in 2011. But the Lions can never be counted on to do anything right. After all, even when they field a statistical juggernaut of a team, they still can't win.

The 1976 Lions ranked No. 12 on the PRD Top 25. Yet those Lions, despite dominating the passing wars that year, somehow managed to stumble through a 6-8 season.

They're the only team in the Top 25 with a losing record. In fact, no other team in the Top 25 lost more than four games.

Perhaps no game in history better exemplified the classic meeting of "irresistible force vs. immovable object" than the 1963 title game between the Bears and Giants.

New York was an offensive juggernaut led by Y.A. Tittle, who set a record with 36 touchdown passes. His mark would stand for 21 years, until broken by Dan Marino in 1984.

The 1963 Bears were -- and remain -- one of the greatest defenses in history. They surrendered just 144 points during a high-scoring year in which the No. 2 defense surrendered 206 points (Green Bay).

Both the 1963 Giants and Bears find themselves on the Top 25 Passer Rating Differential list: The Giants were propelled onto the list by an awesome-for-its-era 94.4 Offensive Passer Rating; the Bears leapt on to the list by virtue of an awesome-for-any-era 34.8 Defensive Passer Rating.

The game ultimately provided evidence for the "defense wins championships" crowd: The Bears won, 14-10, thanks to a defense that handed Tittle one of the most brutal beatings any quarterback has ever suffered. He threw five picks, was twice knocked out of the game, was hastily taped up on the sidelines and famously injected with more needles than a med-school lab dummy.

So Tittle was beaten badly. But the 1963 NFL title game -- like almost every title game in NFL history -- was a resounding triumph for the power of Passer Rating Differential.