The Seattle Seahawks may be in trouble this season.
While the team appears ready to have a big year, NFL history suggests that they will struggle in one key area. That area would be turnovers, or more specifically, the team's ability to get their opponents to turn the ball over.
Over the past decade, there have been 98 teams who have amassed more than 30 takeaways in a season. That is approximately 31 percent of all possible teams, which makes for a reasonably large sample size for this data set.
The 2012 Seahawks were one of those teams, having collected 31 takeaways.
What doesn't bode well for Seattle is the fact that the vast majority of those 98 teams saw a very large decrease in their takeaways the year after collecting more than 30. Just 13 of those teams saw their number of takeaways increase or stay the same.
Here is a histogram showing the data. Notice that most saw their number of turnovers generated drop dramatically:
The median change in takeaways was a decrease of nine. For Seattle, a decrease of nine turnovers created would constitute a loss of approximately 29 percent of their defensive turnovers.
To put it another way, NFL teams averaged 3.24 points off of every turnover in 2012 according to ESPN's Mike Sando. That means that those nine turnovers would be worth approximately 29 points. For a team that played in many close games last year, such a drop in takeaways could have cost Seattle three or four wins in 2012 and would likely have kept them out of the playoffs.
Not only is there a troubling downward trend in takeaways for a team that compiled over 30 in a given year, but teams have also had great difficulty in getting that many takeaways multiple years in row. The Seahawks currently have a two-year run in terms of forcing that many turnovers.
Such streaks are incredibly uncommon. There have been very few streaks in the last decade of 30 or more takeaways in a season.
|Years in Streak||No. of Streaks|
The reason for this trend has very little to do with the teams and players that make these streaks happen. Some stats, like passing yards per attempt or rushing yards per carry, tend to be for individual players fairly stable from week to week and from season to season. These are low-variance stats.
Takeaways aren't like that. A turnover is a high-variance stat. A team might get four in one game then not get any for three weeks. This high variance from week to week can lead to large swings from year to year. Basically, the data contains a lot of randomness, and the season is too short for these things to "average out."
It simply takes a great deal of luck to put one of these streaks together, regardless of the talent on a defense.
Does all of this mean that the Seahawks are guaranteed to get fewer takeaways in 2013? Absolutely not. The data simply suggests that reproducing the results from the last couple of years is very unlikely. The Seahawks will need some luck on their side if their defense is going to generate turnovers at the same rate that they have in recent years.