NFL Injuries Part III: Variation by Position and Age

NFL Injuries Part III: Variation by Position and Age

by Zach Binney

If you haven't read part I and part II of this series, I highly recommend it. Part I lays out what we're trying to do in this four-part series (describe NFL injuries) and gives some important caveats. Part II looks at how injury trends typically change throughout the season, and how they have changed over the years.

Today we have a whole post investigating the complexity of how injuries vary by age. Is a veteran really more likely to miss games as he ages? If so, how much?

Injury Risk by Age

The data in this section (except where indicated) excludes quarterbacks, kickers, punters, and other special teams players. I have done this because these players have lower baseline injury risks and make up a large proportion of players in older age groups (together they become a majority of players 37 and older). Including them would artificially deflate the injury risk for the oldest players.

The denominator for the chart and table below is player-seasons where the player played in at least one regular season game or was on IR the whole year. So all of these injury risks are only applicable for players who were still good enough to play if they weren't injured. A banged-up or washed-up 31-year-old linebacker doesn't make this chart unless there's a good chance he makes somebody's roster. He has to pass a smell test of "would he play if he were healthy?" before the injury risks below apply to him. Everything in the chart is conditional on passing that smell test.

Table 1. Number of Player-Seasons by Age
Age Player-Seasons 2000-14
20-21 172
22 1,256
23 3,111
24 3,790
25 3,479
26 3,017
27 2,544
28 2,091
29 1,760
30 1,413
31 1,078
32 786
33 548
34 328
35 206
36 115
37 61
38 31
39 13
40+ 13


12 comments, Last at 13 Jan 2016, 6:12am

9 Re: NFL Injuries Part III: Variation by Position and Age

It could make for a very interesting multivariate regression or fitting/optimization exercise.

It's unfortunate that as presented the graphs are possibly not of sufficient quality
and clarity to motivate the students.

The standard is the standard!

10 Re: NFL Injuries Part III: Variation by Position and Age

Agreed with everyone else: great series of articles.

Minor point, but I think there must be a calculation error with the grey line (Ages 36+) in Figure 8. That point should be a weighted average of all the points corresponding to ages 36 and above, where the weight is the number of player-seasons for each age. By construction, that weighted average must be less than the maximum and greater than the minimum value observed for those age groups, so it's impossible for the grey line to extend above the rest of the data. That doesn't change the overall point, though.

11 Re: NFL Injuries Part III: Variation by Position and Age


That's a great catch I'm embarrassed to say I didn't make. It was a spreadsheet coding error. In the interest of transparency (hooray, ethics), I want to clarify what Figure 8 should look like (and we'll try to get it changed soon):

Each line that's an older age group should have its final points dropping further and further. So 35+ and 36+ are flat, 37+ is a slight decline, and 38+ to 40+ are all precipitous drops. It doesn't change my central point much since the difference between flat risk and a precipitous drop is a pretty big deal, but my coding error did lead me to overstate the effects of this decision insofar as I can't actually make injury risk RISE by this categorization choice. For that, I apologize.

Thanks again for catching that!

12 Re: NFL Injuries Part III: Variation by Position and Age

Position and Age changes according to time but to maintain it one have to take care of its health. And this can be done with proper guide related body health. This is very important for the sports person specially. is effective for this.