Offensive Efficiency: Turnovers
In my last post about offensive efficiency I showed that there was a correlation between a team’s offensive points per game (PPG) and their yards per drive (YPD). Since the AFL/NFL merger, teams’ PPG can be shown in this equation:
PPG=0.66(YPD) + .048 with an R2 of .6
Now, a lot of things can affect the relationship between YPD and PPG but none more than turnovers. It’s a fairly obvious point: teams which turn the ball over more score less than they should. Here’s the relationship between PPG and turnover percentage (TO%):
It’s not as strong of a correlation as you might think. The R2 for this trend line is only .16 which suggests only a small amount of the variation between teams’ PPG is due to their turnover rate. However if we go back to our YPD vs. PPG analysis we see something interesting. Take a look at the all-time best offenses in terms of TO% (i.e. the offense which turned the ball over the fewest times per drive) and how they stack up in terms of expected PPG based on their YPD:
The two columns all the way at the right show the team’s expected PPG based on their YPD, as well as how much they over/underperformed the expected value. The 2010 New England Patriots turned the ball over less than any team in NFL history and ended up scoring 12.28% more points than you’d expect based on historical trends. The top 25 teams by TO% overperformed their PPG by an average of 9.9% and only 7 of the 25 underperformed. Now look at the 25 offenses that turned the ball over the most:
These 25 offenses underperformed their PPG by an average of 11.1% with only 7 of the 25 overperforming. The 2006 Oakland Raiders stand out as one of the most underperforming offenses of all-time, scoring just over half the number of points you would expect based on the number of yards per drive they amassed. Not surprisingly, they turned the ball over – a lot. 28.57% of their drives ended in a turnover. Not the worst ever, but really bad.
Lastly, here are the best YPD offenses of all time that we saw in the previous post:
What stands out here is that the Greatest Show On Turf (2000 Rams) put up a ton of points but also turned the ball over a ton. How did they manage such a high PPG despite turning the ball over 35 times? Well, they managed to convert an unusually high percentage of their drives (37%) into TD’s – 6th best since 1970. Converting drives to TD’s will be the subject of the next post in this series.