It seems like every fantasy football site out there has a blurb about the fact that Calvin Johnson was tackled eight times within the 5yd line in 2012, more than any other wideout in the NFL. That seems like a lot, right? Especially for an elite athlete like Megatron, who is 15 feet tall, with the wingspan of a jet and hands developed by the Dyson Labs. I think people have latched onto this figure because it seems to provide a reasonable explanation for his measly five touchdowns last year. But how often do pass-catchers get stopped so close to paydirt?
To answer that question, I looked regular season NFL play-by-play data from the 2008-2012 seasons (available at Advanced NFL Stats). In that dataset, there were 52,680 passes completed, of which 1721 instances resulted in a tackle within the 5yd line. As you can see in this graph breaking it down by seasons, these are pretty rare events:
It may not happen very often, but are some players more prone than others? Here’s a list of the guys from 2008-2012 who were brought down the most frequently at or inside the 5yd line after making a catch:
No slouches here! There are a few takeaways from this first table. First, it is abundantly clear that these events are incredibly rare – the guy who was brought down the most near the goal line had it happen an average of 4.4 times a season. Second, Megatron is nowhere near the top of that list – he’s no more susceptible to it than any other top receivers. And finally, only one running back made the list, master of the screen pass Darren Sproles.
So it seems pretty clear that getting brought down near the goal line isn’t something that Calvin Johnson has made a habit of doing, but just for fun, let’s take a look at how his 2012 season stacks up against other single season performances. Here’s a table looking at the 12 highest single season totals for getting taken down within the 5yd line, along with the number of takedowns they had in their N+1 seasons (from the same 2008-2012 dataset):
|Player||Year||5yd line||N+1 5yd line|
Again, I think there are a few things that stick out in this data. First, only one guy made the list in consecutive seasons: Mr. Roddy White, with six occurrences in each of 2011 and 2012. Second, Megatron’s 2012 wasn’t even the worst season of getting caught near the end zone. That honor goes to Anquan Boldin, who was brought down nine times within the 5yd line in 2008. Finally, everybody got better in their N+1 season (again with the exception of Roddy White, who stayed the same).
So now we know that receivers don’t get brought down within the 5yd line very often, that the guys who do get taken down near the goal line are target monsters, and that Calvin Johnson’s 2012 season isn’t something we should expect him to replicate anytime soon.
But the whole reason to do this exercise is to find out whether Megatron’s touchdown numbers are likely to recover next year, and if there’s any way to predict that recovery based on tackles within the 5yd line.
To answer that question, I moved my data from Excel to SPSS, to take a deeper look at the relationship between getting tackled inside the 5yd line and receiving touchdowns. First, I ran a correlation analysis, and found statistically significant correlations between the number of times a guy got tackled inside the 5yd line in season N and receiving touchdowns in both season N (r=.308, p<.01) season N+1 (r=.235, p<.01). This means that on average, guys who are brought down near the goal line score more touchdowns than guys who aren’t going down very often near the goal line, and that this pattern carries over across seasons.
Of course, correlation isn’t causation, so to get a little bit of additional power, I ran a simple linear regression analysis, looking specifically at receiving touchdowns in season N+1 as a function of getting tackled within the 5yd line in season N. The resulting model was statistically significant (p<.001), and gave an equation that looked like this:
Receiving TDs (season N+1) = .549 * Tackles within 5yd line + 2.267
Here’s a figure that makes it even clearer:
Based on this equation, we can make a guess that Calvin Johnson, who was tackled eight times within the 5yd line, will score 6.659 TDs in 2013, which is a couple more trips to the end zone than he had in 2012. Now, that prediction comes with a metric ton of caveats. First, I didn’t control for any of the other factors that affect touchdown receptions, like targets, receptions, team offense, QB, etc. Second, it is only based on the last five years of NFL play by play data, meaning it may have limited generalizability to future data. That’s going to be true about every model built on a small sample of data, but it’s worth repeating here.
Still, it’s nice to know that getting stopped near the goal line isn’t a harbinger of doom for your stud receiver’s future. If anything, exercises like this should be a reminder not to overreact to sexy factoids in the offseason. Looking at some statistics out of context can make them pretty sensational. But if you take a moment to ground them back in reality, often times you’ll find there’s nothing to get worked up about.