Sean Payton returned from his season suspension, looked at his team, and quickly decided that a change on defense was needed. It wasn’t a difficult decision. In Steve Spagnuolo’s first and only year as defensive coordinator, the Saints shattered the mark for most yards allowed in a season ever (7,042 yards allowed). It was over 900 more yards than the next worst team (the Giants). It was almost 600 yards more than the Detroit Lions allowed when they went 0-16 in 2008. It was bad.

Preferring continuity in the face of historically bad results would be lunacy. The question is how much improvement should we expect by switching to a 3-4 defense? Using the pro-football-reference data on games started to identify teams playing 4-3 defense vs. 3-4 defense, I found all teams that switched defenses from year to year. The average change for teams switching to a 3-4 defense since 2000 was to go from being ranked 20th in points allowed and 19th in yards to 15th in points and 17th in yards allowed in the first year of the switch.

Of course, New Orleans isn’t a typical team switching, as they were a really bad defense. We also need to control for how much improvement all teams naturally show (the old regression to the mean). Here is a summary of how teams switching defenses versus staying with the same type of defense have fared, among those that finished in the bottom ten in both points allowed and yards allowed the previous season.

There were only eight switches to a 3-4 defense that qualified, compared to 80 bottom ten defenses that stayed with the same defense. Houston with Wade Phillips was the most successful switch, going from the bottom of the league to top ten in both yards and points in 2011. To have that impact, the Saints better find the next J.J. Watt, a 3-4 end perfect for the defense who can also disrupt like few at the position. The average result shows that the teams that have made the switch when their defense was bad have had more improvement the following year than other similar defenses.

In the case of New Orleans, if the New Orleans Saints get the average impact that teams switching to the 3-4 defense have received, they will be Super Bowl contenders again in 2013. New Orleans has rarely had a good defense in the Sean Payton era. When they have been merely closer to average than horrible, they have been contenders. In the three seasons since 2006 when New Orleans has ranked in the bottom 8 in points allowed, they have never had a winning season. In the other four seasons, they are a combined 47-17 with four playoff appearances, two trips to the NFC Championship Game, and one Super Bowl title.

It remains to be seen whether linemen like Cameron Jordan and Akiem Hicks (sizewise, more likely to 3-4 DE than OLB) and Sedrick Ellis (possibly to NT) can make the switch. Junior Galette, an undersized defensive end, could be the wildcard in this move, converting to a 3-4 OLB. He’s flashed potential as a role player, registering 5 sacks last year. Whether that personnel, with a couple of additions, can turn it around remains to be seen, but it cannot be worse than it was. If they can get to average, the Saints will be marching again in 2013.

[photo via USA Today Sports Images]