After OCC's fantastic article showing historically bad defenses tend to trend upwards the next season, I planned on writing a follow up piece, using the same methods with different data points, namely points per game or PPG and DVOA. I wanted to see where Dallas ranked last year, then see how similarly ranked teams fared the next season. After reading some of the comments from OCC's article, and getting into the research however, the article started going in a different direction. Instead I'll be looking at some of the main questions regarding our defense and what the historical data has to say about them.
One quick note: I'll only be following data back to the 2007 season. For many reasons I view 2007 as the beginning of the modern NFL offensive era. The rule changes that went into effect after Patriots DB's mugged Indy's WR's in the NFL playoffs had gone into full effect. The 2007 Patriots set all kinds of offensive records. Five of the top 10 NFL offenses came in 2007 or after (the 11th ranked offense came in 2010). So I'll only be going back to 2007. It lowers the sample size, but I think it gives a more representative set of data for the modern NFL.
WHY DID TEAMS REBOUND?
One of the most common comments I saw in OCC's article was some variation of "why?". Why did most of the teams OCC listed rebound? Let's look at the changes each team made from one year to the next.
2012 New Orleans Saints: Perhaps none of the teams we'll examine here had as much change from one year to the next as the Saints. In 2012 the Saints coaching staff was a mess. Head coach Sean Payton was suspended for a year over BountyGate. The head coaching duties were split between Aaron Kromer and Joe Vitt. The team never really had a chance. They put up the worst defense in the league and sputtered to a 7-9 record.
Major changes occurred in 2013. Sean Payton returned as head coach. Rob Ryan replaced Steve Spagnuolo as defensive coordinator and swapped the 4-3 for the 3-4. The team jettisoned a number of defensive players, including long-term standouts Will Smith and Roman Harper, then spent a first-round pick to draft safety Kenny Vacarro. All told the Saints brought in five new defensive starters. The changes worked, as the Saints defense jumped from 32nd to fourth in the league, and their record went from 7-9 to 11-5.
2011 Green Bay Packers: Despite having the worst defense in the league the 2011 Packers posted the league's top record at 15-1, so it makes sense that there were minimal changes to the team. Dom Capers kept his job and his defense. The team had four new starters in 2012. RDE C.J. Wilson was hurt for most of 2011. New starters Jarrett Bush and D.J. Smith were already on the team in 2011. The biggest change might have been moving future HOF Charles Woodson from corner back to safety. Despite only making minor changes, the team's defensive ranking jumped from 32nd in the league to 11th - which probably tells us more about the highly variant nature of defensive rankings than anything else.
2010 Denver Broncos: Like the 2012 Saints, the 2010 Broncos were a team in disarray. Head coach Josh McDaniels had alienated his team, his owner and his fan-base. After a 4-12 season, wholesale changes occurred in 2011. Gone were the head coach and defensive coordinator, replaced by John Fox and Dennis Allen respectively. Gone was the 3-4 defense, replaced by the 4-3. 2011 also brought seven new starters, including Elvis Dumervil, (returning from an injury that kept him out all of 2010), and their new first round pass rusher, Von Miller. Denver's defense improved from 32nd in the league to 20th, and their record improved four spots, going from 4-12 to 8-8.
2009 Detroit Lions: The 2009 Detroit Lions were yet another team in disarray. Coming off the first winless season in NFL history, and their second consecutive year of being the worst defense in the NFL, the Lions cleaned house. Rod Marinelli and Joe Barry were gone as head coach and defensive coordinator, replaced by Jim Schwartz and Gunther Cunningham. The 2009 Lions replaced every defensive starter from 2008 according to PFR, and this was after replacing seven defensive starters from 2006-2008. What did they get for all this change? Another year as the worst defense in the league.
Year two of the new defense showed some marked improvement however. The Lions replaced seven more defensive starters, and spent a high draft pick on standout rookie Ndamukah Suh. They replaced nearly the entire front four, and only kept FS Louis Delmas in the backfield. These changes resulted in an 11 spot jump in the defensive standings, from 32 to 21.
What Does it All Mean?
Honestly? Probably nothing. As OCC noted in his article, defensively, YPG has very little correlation to winning. The 2012 Saints team is something of an anomaly, with Sean Payton's suspension and the BountyGate scandal. The same could be said of the 2010 Broncos, Josh McDaniels was a historically inept head coach. The 2011 Packers barely changed anything about their team, saw their defensive ranking jump 21 spots, and their actual number of wins drop by four. Detroit on the other hand spent years churning their roster, brought in a new head coach and a new defensive coordinator, and it still took two years to see any change. About the only constant among these teams is bringing in a first-round defensive player, and Green Bay didn't even do that.
So as fans, what should we be thinking? For starters, ignore the "worst defense in the NFL" remarks. There are two reasons. One, YPG doesn't seem to be a good indicator of how bad or good a defense really is...at least not when it comes to winning games. Second, we are in, for all intents and purposes, the "juiced ball" era of NFL offenses. Until someone finds a way to normalize stats across different NFL eras we will continue to see "historically" bad defenses, and "historically" good offenses. It doesn't really tell us much.
That's not to say that everything is rosy in Cowboy land. We still had a bad points per game average, and most advanced stats ranked our defense poorly. If we want to improve our team and our defense let's look at stats that actually correlate with winning, and find ways to improve in those areas.
Coming in Part II: A look at what defensive stats actually correlate with winning. Also, the Linehan effect on defense.