Game Scripts, Part II: Analyzing team seasons

Yesterday, I rolled out Game Scripts, a way to measure the flow of every game since 1940. The sum of each team’s Game Script in each game can be used to give us an average Game Script score on the season. You might think that this number would be a good proxy for how dominant a team was, and that’s largely true: the teams with the highest game script scores tend to have been the most dominant teams. However, there are some reasons to be cautious with this approach: game scripts are not adjusted for strength of schedule and in any given game, the losing team can end up with a better score than the winning team. That said, here are the teams with the highest Game Scripts since 1940:

The teams with the highest game scripts last year? Green Bay (7.4), New Orleans (5.6) and Houston (5.4), while the Rams (-6.4), Colts (-7.2), and Bucs (-8.7) were at the bottom of the league. But let’s get to the real point of using Game Scripts — to help put passing and rushing ratios in context.

Last year, the Buccaneers had the second highest effective pass/run ratio in the league (defined as total pass attempts divided by rushes plus total pass attempts, but with all kneels and spikes excluded). But that’s misleading, because Tampa Bay had the worst Game Script in the league. Conversely, were Houston and San Francisco really the second and third most run-heavy teams in the NFL last year? The table below lists each team from highest to lowest pass/run ratio:

But we need to consider the passing ratios in light of the Game Scripts. Teams like Green Bay and New Orleans, and to a lesser extent New England, Atlanta, and Pittsburgh would have passed much more frequently if they weren’t racing out to large leads. Think back to the ’99 Rams, the first edition of the “Greatest Show on Turf” and the only team to win the Super Bowl. You surely think of them as a pass-heavy team, with Kurt Warner, Isaac Bruce, Torry Holt, Marshall Faulk, Az-Zahir Hakim and Ricky Proehl. In 1999, NFL teams passed on 57.1% of all plays. The ’99 Rams passed on 56.6% of their plays that season. That’s right: if so inclined, you could paint a picture that the ’99 Rams were more of a running team than a passing team.

An even more recent example would be the ’07 Patriots. On average, teams passed on 56.6% of plays in ’07; the high-flying, 16-0 Patriots passed on 57.4% of their pass plays, barely more than league average. These odd results happen every season, including 2011. Would you have guessed that the Cardinals and pre-Robert Griffin III Redskins both passed on a higher percentage of their plays than the Packers?

Controlling for a team’s pass/run ratio based on their Game Script is difficult, since they involve completely different units. There is a solution to this problem, although watch out: it involves math. What I did was calculated the standard deviation for each of these metrics to come up with ratings that are similar in meaning to PFR’s passing index numbers. A score of 115 means a team is one standard deviation above average; a score of 85 means a team is one standard deviation below, 70 means two standard deviations below, etc.

How do we calculate them?

• For game scripts, the average is always zero. For each league and for each season (so as to not combine the NFL and AFL) since 1940, I computed the standard deviation of game scripts among teams. This was necessary because, as you would expect, the standard deviation used to be considerably higher than it has been over the past 30 years. For each team, the formula is: 100 + 15 * (Game Script Average / Standard Deviation for all teams that season).

• For pass percentage, we use a similar formula, except the average is not zero. So the formula is: 100 + 15 * ( (PassPercentage – LeagueAveragePassPercentage)/(Standard Deviation for all teams that season) ).

Let’s re-look at the 2011 standings, but this time, I’m going to include their Pass Index and Game Script Index numbers (based on standard deviations above average), and sort the table by a column I’m calling Pass Identity.

Looking at the top row, the Packers had 590 pass attempts and ran 373 times. They passed on 61.3% of their plays, and had a game script of 7.4. So this was a team that passed a lot even though it was frequently ahead in games, often by double digits. The Packers were nearly one standard deviation above average in pass percentage while being over two full standard deviations above average in terms of Game Script. That’s what the numbers in the next two columns represent. So how do we judge how pass-heavy an offense is? The Packers pass ratio was 11 units above average, despite a season-long game script that was 32 units above average. Because we’ve converted game scripts and pass percentage into the same units, we can simply add the two, to measure how pass-heavy an offense was. That makes their passing identity 43 units above average, meaning no team was more pass-heavy than the Packers last year. The Saints weren’t far behind, with the Lions and Patriots up next. That passes the smell test.

That’s the point of Game Scripts. We can measure offensive philosophy much more acutely by understanding the flow of the game. When teams are passing even when they’re leading, that’s a team that’s passing by design, not necessity.

In 2007, the Patriots ranked 14th in the league in pass to run ratio. But using the “Pass Identity” formula described above, New England had a score of 49, highest in the league and the fourth highest of all-time. The ’99 Rams ranked 18th out of 31 teams in pass percentage. But they had a Pass Identity grade of 36, highest in the league.

When I developed Game Scripts, the goal wasn’t to create a new stat to tell us something we didn’t know. Instead, my intention was to create a stat to help us empirically show what we already know. The goal isn’t to wow anyone by saying that the ’99 Rams and ’07 Pats passed a lot, but rather to adjust the stats to show how that was the case. By that measure, I consider Game Scripts a success.

What teams had the truest passing identity of all-time? The 1995 49ers were a great team. They had the highest Game Script in the league that season, at 7.7. They outscored their opponents by 199 points, over 50 points more than the team with the second-best points differential. Yet they called 677 passing plays, and finished with the sixth highest pass percentage in the league.¹ This was also the year that Jerry Rice set the single-season receiving mark. With a game script of 138 and a pass ratio of 116, the 49ers had a Pass Identity of 53, just edging out two Run-n-Shoot Oilers teams for #1 on the list. There aren’t too many surprises at the top, as the ’07 Pats, ’79 Air Coryell Chargers,, the ’01 GSOT Rams, a couple more Run-N-Shoot Oilers teams, and last year’s Packers teams are next.

We can also use game scripts to measure the most run-heavy teams. We often think of run-heavy teams like the ’90s Cowboys or ’60s Packers, but that’s because they were so frequently playing with leads. For bad teams with a low Pass Identity, it may be a better indicator that the quarterback was just really, really bad.

You shouldn’t be too surprised at this list then, either. The most run-heavy team after adjusting for situation was the Tim Tebow 2011 Broncos, followed by the ’72 Bears, with Bobby Douglass at quarterback. The ’72 Bears were a bad team, but they had the fewest pass attempts in the league along with the lowest pass percentage. You probably aren’t surprised to see a Cowboys team with Emmitt Smith high on the list, but I doubt it was one of the ones you were thinking of. Rather it was the ’01 team, in Smith’s penultimate season in Dallas. The Cowboys alternated between Quincy Carter, Anthony Wright, Ryan Leaf and Clint Stoerner at quarterback. Dallas wasn’t very good, and ended the year ranked 30th in points. But Dave Campo’s team ranked last in pass attempts and third in rushing attempts, despite an average Game Script of -3.5.

If we look at just teams with positive game scripts, we get a more familiar look at the most run-heavy teams. The team with the strongest rushing identity? Rex Ryan’s ground and pound 2009 New York Jets:

1. Note that for years since 2000, I removed spikes and kneels, but for years prior to 2000, I used the more familiar data available at PFR. [↩]

Tagged as: Don Coryell, Emmitt Smith, Game Scripts, Jerry Rice, Mike Martz, Rex Ryan, Tim Tebow