In a previous post, I detailed how the 3-4 defenses over the past 10 seasons have, on average, outperformed 4-3 defenses. However, it’s possible that those 3-4 defenses simply had better players and that the 3-4 only appears to be the better scheme.
This time around, to account for each individual defense’s strength, I used a multivariate regression. The dependent variable in each model was a measure of success—EPA, WPA, and Success Rate (SR). The variable of interest was whether or not the defense was a 3-4 (a 1 if it was and a 0 if it wasn’t). The resulting coefficient of this variable represents the advantage of the 3-4 over the 4-3.
Each individual team was also assigned a dummy variable intended to capture the team-specific strength of their defense. Conveniently, this technique also accounts for the general year-by-year improvement in the effectiveness of NFL offenses.
There were 318 cases (team-years), from the 2000 Arizona Cardinals...to the 2009 Washington Redskins.
The results of the regressions indicated that the advantage of the 3-4 was not due to a coincidence of exceptionally talented players who happen to play in 3-4 schemes. In fact, the advantage of the 3-4 is even larger when individual team strength is accounted for.
This time, in addition to comparing WPA and EPA, I compared the 3-4 and 4-3 in terms of Success Rate (SR). SR is defined as the proportion of plays that result in positive EPA. Although it is a simple derivative of EPA, it is important in how the teams themselves perceive the game, a concept I'll explain in a later post.
Here are the key results of the regressions. Like before, negative numbers are better. Spikes, kneel downs, and aborted plays are excluded. The resulting coefficients for the 3-4 defenses were significant at the 0.05 level, except those noted by an asterisk, which were significant at the 0.10 level.)
Advantage of 3-4 In:
SR vs. Pass
SR vs. Run
EPA vs. Pass*
EPA vs. Run
WPA vs. Pass*
WPA vs. Run
Contrary to the results seen in part 1, the regression results suggest the strength of the 3-4 is against the pass, although not by much.
Teams all around the league are switching to the 3-4 for a reason, and the stats appear to back up the belief that it's a better scheme against the modern NFL offense.