Your recent post that mentioned the pass-happy ways of Josh McDaniels got me to scrounging around in my records and I found a few things that might interest you. The idea of pass-happy, to my thinking, has to involve what exactly the averages are and what is, therefore, unusual or extraordinary. Here's what came to light.
Let's take a quick wormhole back to the 1960s. Pro football emphasizes a power running game, and for good reason. Rushing plays outnumber pass plays by a margin of 59% to 41%, industry-wide. Why? It's simple - pass plays produce 4.8 yards per play, on the average. Running plays only produce between 3.9 and 4.3 yards per play. So - for the extra .3 yards per play, why not pass?
It's because passes are being intercepted at a rate of 6%. Fumbles, on the other hand, are occurring at 3%, and it doesn't take a lot of interceptions to wipe out any advantage in length of play. You also have the fact that this is the pre-holding era - offensive linemen can't hold with their hands inside the defenders shoulders, and as a result you have both a higher number of sacks (although the stat isn't being kept yet) and a higher number of injuries for starting QBs. Rushing is just a better option, and the league focuses on it. But things start to change and for a lot of reasons.
There's little doubt that the biggest change comes about in 1978 when the league makes it legal to grab for O linemen and they no longer run around the field with triangles hanging from their shoulders. It wasn't the only change that was taking place - that rule was altered in part because the league understood that passes are exciting, scoring is exciting and excitement builds franchises (and bank accounts) - but it was a huge change nonetheless. There was one other major factor taking place that made a huge difference and the Chargers were ground zero for that area of growth. It goes back to Sid Gillman, brilliant strategist that he was, and to those who studied his work on passing.
It is surprising, in part, that Gillman hasn't gotten the kind of recognition among fans that other name achieved. Certainly, his schematic descendant, Don Coryell, earned a lot of what he has received, but it was in the genius of Gillman that the ideas of stretching the field - vertically and horizontally - came into common usage. Al Davis, Don Coryell and Bill Walsh were the three who studied Gillman's approach the most intently. Gillman's work was complex and not everyone was interested in a strong armed passing approach back then, for the reasons that I elucidated. But that was all to change...
Coryell's work is probably common knowledge among Chargers fans and for good reason. But while both Davis and Coryell took mostly their vertical passing approaches from Gillman's work, it would be Walsh's inventions that would probably change the passing game the most. That came about in the mid 1970's due to a little know QB by the name of Virgil Carter. You see Virgil, unlike most (all) modern QBs, really couldn't throw the danged ball more than 10-15 yards, but was accurate in that area. And Walsh, stuck as an offensive assistant with Cincinnati, was given the responsibility of creating an offense that could use him, since Cincy didn't have anyone else. That was where the league started to change.
To maximize production from Carter, Walsh decided to stretch the field horizontally. He came to the realization that the idea of throwing to a receiver who was not there yet - timing routes - could be nearly unstoppable if the pieces each played their role. Clearly, this has had a dramatic impact on much of the modern game; although only about a third of the teams currently play a 'West Coast Offense' (the definition of which is under substantial attack), using the concepts of stretching the field horizontally and/or even more commonly, extensively using timing routes, has become commonplace in the NFL. In fact, Bill Polian of the Indianapolis Colts said,
"In (a) sense, everyone in the NFL today is running Bill Walsh's offense. Because the rhythm passing game is all Walsh."
Walsh knew that these short, timed passes could be effective against any defense that was used during this time. Later, part of the reason for the modern Cover-2 formation, which stretches the zone of the MLB and plays zone coverage by the CBs (hence the name Cover 2 - pass coverage in the 2nd level), was to defend against this offense. The system as Walsh developed it used receivers who ran routes exactly geared to how many steps back the QB took - one set of routes for a 3-step drop, a different set for the 5-step drop.
From Walsh's perspective, back in his days with Cincinnati, it was all about having a chance. His job was on the line: he had to find a way to win with the pieces that he had. He believed in offensive strategy. He just needed to make his players effective. But it changed the NFL for all time. The modern passing game was on its way, and soon the league was making other changes to encourage the scoring offenses that they believed would put players in the endzone and fans in the seats. Walsh would go on to considerable fame, but his time and effort at improving the mechanics and decision-making of Dan Fouts alone is worth a footnote in Charger lore.
By the mid 1990s, the percentages had reversed themselves. Rushing plays now accounted for about 41% and passing for 59% of all plays. That hasn't changed, much. I've only got figures up to 2005, but over that time, the percentages stayed about the same. Running plays would bring in 3.9-4.3 yards per play. Passing, however, had grown to about 7.7 yards per attempt, and that made a huge difference. Because of that, the NFL average has remained about the same - 57-59% (variable by year) passing and 41-43% rushing. A more thorough accounting of this transition can be found here if anyone cares to peruse it.
What is even more important is that interceptions have dropped to the same level as fumbles - about 3%, with minor variations by year. Since passing is more productive and no less dangerous to ball control (in the sense of INTs to Fumbles), it has made sense for the leagues teams to go to a pass dominant overall scheme. Obviously, there are teams like Chicago that claim to get off the bus running and teams that throw no matter what (Denver was one last year), but the leagues averages have stayed very close to the numbers I've listed above. I'm taking them from Michael Lewis' The Blind Side and from the Journal of Quantitative Analyses in Sports (Ben Alamar), by the way, in case someone comes up with different numbers at some additional source. Some of the info on Walsh came from Dr Z at Sports Illustrated - there were several sub-sources on Walsh and his influence, but the numbers were only from those two sources.
The reason that this came to light is that Josh McDaniels is just average when calling passes versus the run. Over the 4 years that he called the plays for the New England Patriots, he averaged 56.9% pass and 43.1% run - just inside the NFL averages. He's not, apparently, the pass-happy guy that he's been painted as. I know - I used to think that same thing. As is often the case, it's those nasty facts that spoil such lovely theories. Someone should do something about that, but until they do - McDaniels is just a middle of the road kind of coach, when it comes to the run/pass percentages. By the way - Jeremy Bates called the Broncos plays last year and he truly was a pass-happy guy. Other than Jay Cutler, you would be hard-pressed to find any fans who mourned his professional passing. He's likely to be great in college ball, though. (Find the McDaniels' stats in Part II here)
Thanks to all. I enjoy and appreciate the writing here and I hope this contributes. Since Gillman was the source and Coryell and Walsh were the students from whom many modern forms have emerged, I thought that Chargers fan's might be interested in a short treatment of how our modern game has come about. Best to all.