There is zero correlation between size and injury rate, and if anything smaller players are less injury prone.
A look at what really correlates with injuries in the NFL using analysis from Football Outsiders
www.hogshaven.com
Are smaller players more injury-prone?
There are many ideas about what makes a player more injury prone, and many people point to size as a possible culprit. Namely, some people claim that smaller players are more likely to get injured playing football because their bodies are less suited to handle NFL collisions. This is at least a fairly straightforward question to study, as
originally done here. However, we should separate this by position group, as we saw in Part 1 of this series that different position groups have different rates of injury, and more mobile positions (RB, WR, DB, LB) tend to have the highest rate of injury, while less mobile positions (OL, QB) tend to have the lowest rate of injury. The overall injury rate by position is summarized in the table below. Remember than an Athlete Exposure (AE) is defined as a game played or a practice session in which a player was listed as a full participant.
Injury Rate By Position
Position | Injury Rate per 1000 AEs (Standard Error) |
---|
RB | 20.7 (0.5) |
DB | 17.4 (0.3) |
WR | 17.1 (0.4) |
LB | 17.1 (0.3) |
TE | 16.9 (0.5) |
DL | 15.1 (0.3) |
OL | 12.8 (0.3) |
QB | 8.6 (0.4) |
ST | 4.4 (0.3) |
Total | 15.1 (0.1) |
Clearly, if we just looked at injury rate vs weight, it would appear that smaller players are more likely to be injured, but that is only because the most injured position groups happen to have smaller, more mobile players. Having established this baseline, we can then plot the injury rate vs weight for each of these position groups.
For the most part, it actually looks like
smaller players are less likely to be injured, not more likely. However, each graph has a slightly different pattern that is worth describing.
- DB is perhaps the easiest plot to interpret, and shows a clear increasing risk of injury based on size.
- DL shows a similar pattern, but the effect is not as large and it is overall a much flatter plot, indicating size is not strongly correlated to injury for DL. The up-down-up shape of the curve may be due to conflation of DEs and DTs.
- LB actually shows a slightly decreased risk of injury for larger LBs up until the heaviest weight category, which has significantly increased risk.
- OL shows a clearly increasing risk of injury based on size, except for the highest weight category, which has greatly decreased risk of injury (this may be the threshold at which OL can simply win with size).
- QB also shows a clearly increasing injury rate based on size.
- RB shows an increasing injury rate based on size up to a point, then a decreasing injury rate. This pattern may again be because two slightly different position groups (HBs and FBs) are being lumped in the same category together.
- TE also shows an increasing injury rate up to a point, then a decrease. It may be due to larger TEs being used primarily as blockers rather than pass catchers.
- WR shows a strong correlation between increased size and increased rate of injury, although the very smallest weight category of WR also had an increased rate of injury.
Overall, these data seem to indicate that smaller players are actually a bit less prone to injury within a given position group, although
usage seems to play a much bigger role than size in determining injury rate. My big takeaway from this is not that teams should target smaller or larger players, but rather just that teams should not assume that smaller players are more prone to injury, as
injury history is a much better predictor of future injury than size. Players like Russell Wilson and Christian McCaffrey are perfect examples of undersized players who were healthy in college