Sorry for the recent absence, I returned from Beirut and went right into recruiting season.  Once I’ve accepted an offer I’ll start posting again. In the meantime, I’ve got a guest post (unedited) from Jared Cohen (previous posts include the 4th down chart and the kick return strategy post).  You can find the original here. and follow the author on Twitter @jaredscohen.

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Given all the animated discussion over the Patriots tactics against the Ravens in their divisional round playoff game, I thought it would be as good a time as any to post some gamesmanship research.

If you read about the game – you know the Ravens were a bit upset with the Patriots usage of receiver eligibility to disguise their offense. The response from the Patriots was, well, Patriots-like. If it’s not against the letter of the law, it’s all good (unless it’s videotaping other teams, in which case even the law doesn’t matter).

Clearly, the NFL is a league where teams will look for any edge, even if it means pushing the bounds of fair competition.

So it’s with that issue in mind that I started digging into the possibility that players are faking injuries.

As a Philadelphia sports fan, I’m generally inclined to assume that my teams will ultimately lose, and so once the Eagles started running Chip Kelly’s offense, I was quick to accuse every injured defender a liar and a cheat (not to their faces of course).

The Eagles run a very high-tempo offense, one that doesn’t allow opposing defenses to leisurely make substitutions or get a full play clock to catch their breath. It’s a major feature of their strategy, and one that opposing teams would love to minimize, particularly if they aren’t well prepared for it.

One way to slow down the pace of the Eagles offense would be for an opponent to use their timeouts while the Eagles offense is in full-swing. But since a team only has three timeouts per half, they’re a little too valuable to burn. An injury however, is an official’s timeout – these are unlimited – and there’s no cost to the injured team outside of the last two minutes of a half, except that the injured player must sit out for the next play.

So in the current NFL world where fake injuries don’t have a cost (apart from having the ‘injured’ defender miss a play) and can help defenses maintain an easier pace – you could see why an Eagles fan might look at an opposing defender’s injury with suspicion.

Could the Eagles opponents be faking injuries to slow them down? The idea is one that makes the rounds in Eagles bars, but one that’s hard to actually evaluate. So this is my attempt to try.

Others have analyzed NFL injuries via metrics like games lost (i.e., players who aren’t active on game day because they’re injured), but to my knowledge, this is the first attempt to use play-by-play data to look at in-game injuries for trends and whether teams might be faking against the Eagles or other high-tempo teams.

The analysis is a bit long, so below are some quick takeaways:

– The Eagles suffered (or inflicted depending on your point of view) the most defensive injuries against the in league in 2014, and are 2nd in the league when adjusted for a per-play basis
– Across the league, there is a significant positive correlation between running more offensive plays and a higher per-play rate of defensive injury
– Such a correlation could be attributed to fatigue, but this correlation does not hold for the three other possible game situations (own offense, own defense, offense against) – these show no strong relationship between running more plays and a higher per-play rate of injury
– Taken together, these last two points support my hypothesis that players fake injuries against higher tempo offenses

Data Collection and Methodology:

I gathered play-by-play data from all the regular season games this year, and identified all the in-game injuries noted in the descriptions. In case you haven’t read play-by-play before, each play has its own line and explanation, and any play that resulted in an injury timeout is noted. Below is an example:

2-10-DET 40 (14:05) (Shotgun) 10-E.Manning pass incomplete deep middle to 80-V.Cruz (27-G.Quin). DET-27-G.Quin was injured during the play.

If an injury was noted as a stoppage, it was recorded. In an ideal world, we’d eliminate injuries that are serious and clearly not fakes, but there’s no detail on the injuries in the game data, so we have to take the major with the minor.

The play-by-play injuries were then coded as to whether they occurred to the offense, defense, or on special teams (e.g., kick coverage). There were approximately 700 total observations, and while it’s possible that not all injuries were noted in the play-by-play data, this is the only comprehensive source for such information. Given that there are ~700 injury stoppages in our set, that works out to 2-3 injury timeouts per game, which sounds possible but could also be low. It’s possible that whoever officially creates the play-by-play gets lazy and misses some, my assumption here is that if any injuries are somehow missed, they aren’t biased towards one particular side of the ball.

After gathering the data, one additional adjustment is for play frequency. Simply put, the more snaps a player gets, the more likely they are to sustain an injury. Therefore, any team that runs more plays is more likely to see a higher absolute number of injuries. To account for this, I also looked up the total number of plays for each team’s offense and defense during the course of the year – to understand the rate of injury rather than the total number.

Output:

Let’s start with the absolutes. I found 692 injuries in the play by play data, 66 of which were special teams plays. I took these out, because they aren’t central to the question of are teams faking injuries to slow down offenses. Of the remaining injuries, I looked at whether they happened to an offensive player or a defensive player and which team they occurred against, below is the data from this season:

Not a shocker to see the Eagles at the very top of that list, and indeed they led the league in defensive injuries against this season.

However, as I already noted, this metric can be misleading. The Eagles offense runs more plays per game than any other team, so we would expect them to be near the top of this list. We need to adjust our data for the number of offensive plays – and we can examine the rate at which opposing defensive players get injured against the Eagles and whether they are still an outlier.

So as we see when we look at it on a rate basis (number of injuries/number of total offensive plays), the Eagles are still close to the top of the league, and roughly 50% above the league average. Houston is just above them, and while no one would consider their offense up-tempo, the fact that the Eagles are so high would be consistent with the theory that opposing teams might be faking injuries to slow them down.

Now, before we get any further down the faking rabbit hole, what if there’s a simpler explanation that doesn’t involve fake injuries? There’s another obvious possibility to explain why the Eagles are so high in defensive injuries against. What about the idea that as you run more plays, players get more physically exhausted, and therefore are naturally more susceptible to injury?

That seems possible, right? So let’s examine that idea a bit.

The first thing we can do is very simple, does injury frequency vary by quarter? If teams get physically tired during the course of the game and that leads to more fatigue and more injury, there should be more injuries as the game goes on:

Interesting. This sort of muddies our waters a bit.

In absolute terms, the number of injures rises dramatically as the game goes on. Injury stoppages in the fourth quarter occur at 2x the rate they do in the first quarter. Part of that can be explained by the fact that the clock stops more frequently in the fourth quarter than the others (and thus more plays), but that wouldn’t explain a 2x difference. I would want to check against the sheer number of plays run by quarter, but I don’t have that data without a bunch of more work.

Still – it looks like that thinking may be reasonable, injuries increase as the game goes on. But it’s also interesting to note that the increase is much more pronounced on the defensive side of the ball. We’ll come back to that later.

For the time being, let’s move on to looking for evidence of fake injuries.

As a general framework for this analysis, I’ve split the types of injury stoppages into four buckets:

1. While on defense, your own team suffers an injury (Own-Defense)
2. While on defense, your opponent suffers an injury (Opponent-Offense)
3. While on offense, your own team suffers an injury (Own-Offense)
4. While on offense, your opponent suffers an injury (Opponent-Defense)

We’ve been focused on bucket #4 thus far, and saw that on a per-play basis the Eagles are close to the top of the league in terms of defensive injuries against on a per-play basis. We also saw that overall injuries increase as the game goes on – but it seems much more prevalent on the defense, which is the side that would be interested in faking injuries.

So can we look a bit deeper to see if play frequency increases injury risk across each type of injury stoppage? The idea that running more plays increases the rate of injury should not be exclusive to offense or defense – although it appears that way at first glance – it’s hard for me to believe that defensive players are in any worse shape or take any harder hits than offensive players.

To take a look at the issue, I ran some basic correlations across each of those four injury types, looking at the number of plays run and the rate of injury. Just to clarify, I summarized the four below:

1. Your defense runs more plays and gets injured more often (this would be a bad defense)
2. Your defense runs more plays and your opponent gets injured more often
3. Your offense runs more plays and gets injured more often (this would be a good offense)
4. Your offense runs more plays and your opponent gets injured more often

Again, if the rate of injury increases with more plays, we should see relationships in each of these situations. So what do we see?

#1 – So earlier we saw defenses suffering more injuries as the game goes on…and yet, when we look at number of defensive plays per game and the rate of defensive injury, there really doesn’t seem to be any relationship. Teams with defenses that are on the field a lot don’t seem to get injured at a higher rate than those who execute fewer plays.

#2 – Our next picture shows a similar lack of correlation, this time between defensive plays per game and the rate of opponent offensive injury. This idea would be that if an opposing defense is really bad, your offense gets more plays, and might get hurt more frequently. But the data shows nothing that looks like a relationship.

#3 – Now we’re on the offensive side of the ball, looking at whether an offense that runs a lot of plays suffers a higher rate of injury. There’s actually a relatively weak negative correlation between running lots of offensive plays and suffering offensive injuries. If you want to believe in things like Chip Kelly’s Sport Science program, you would expect a negative relationship as teams that employ high tempo offenses are more adequately prepared to stay healthy while running it. While a very slight relationship exists, it doesn’t look to be that large, if it even exists at all.

#4 – Hmmm…now it’s officially interesting. When we look at the rate of defensive injury against offensive plays per game, there is our most significant positive relationship. A correlation of 0.39 is significantly more than we’ve seen in the other three instances, and it’s also the only one where there is a clear incentive to fake injuries.

Taken alone, this relationship might be explained by the fatigue theory, but I think it’s tougher to make that argument when you don’t see anywhere close to the same relationship in all other situations. When a defense is bad and on the field a lot, they don’t get hurt more often, when an offense is good and runs lots of plays, they don’t get hurt more often, and when a defense is bad and their opponent runs a lot of plays, they don’t get hurt more often. The only ones who show a substantial increase in injury stoppages as plays increase are opposing defenses.

To me, that’s pretty freaking suspicious. Either opposing defenses are the only ones who suffer from fatigue-related injuries…or maybe some of the injuries aren’t injuries at all.

Now, this is far from 100% conclusive. It may be that defensive players naturally get more fatigued than offensive players due to their roles (i.e., offensive players can take more plays off because they know the play calls)…but I don’t really buy that. I think there’s at least a little bit of shenanigans.

It’s also an entirely different question as to how much this even matters. Any fake injury will happen on the margins, as you see the number of total injury stoppages remain relatively small (2-3 total per game). But for an Eagles team that narrowly missed the playoffs, the marginal differences matter.

Solutions

So is there a way to address teams that fake injuries? There are certainly options, but some of them are just impractical. The NHL has a penalty for diving, but you really can’t ask the officials to diagnose injuries and try to penalize fakers. You could charge a team a timeout, which the NFL already does if an injury occurs in the last two minutes. That’s much easier than trying to penalize teams, but also provides incentive for coaches and players to hide injuries (also, what do you do in the case of a ‘Body Bag Game’?)

One idea I think might actually be workable, is to tweak the NFL’s current rule for injured players. As it stands today, an injured player who causes a stoppage has to miss at least one play. Well, if you want to eliminate fake injuries, you should raise the cost to those players for faking, and you can do that simply by making them sit out longer. What if, when a player is injured and causes an official stoppage, they must sit out not for just one play, but for the remainder of that series or until a change of possession?

Missing the rest of a series is a bit more significant than missing just one play, and is something that could balance the equation on faking injuries. It also dovetails nicely with the NFL’s stated emphasis on player safety (interpret my use of the term ‘stated’ as you will, based on your own level of cynicism)

If there are fake injuries happening, such an increase in missed time might be enough to keep anyone from acting hurt. Requiring a player to miss the remainder of a series also isn’t as significant as forcing them out for the rest of a quarter or a game.

Some would argue that this isn’t even a problem worth focusing on. But if fast-paced offenses gain greater acceptance in the NFL (which will happen if more of them succeed), the issue will only become more prominent (beyond the realm of the paranoid Eagles fan) and could materially impact the game.

Summary Data

Below is a table of all the raw data I used here, as a reference:

Bonus – Jevon Kearse All-Stars

One last thing I did with this data, after pulling it together, was dig through and sum up all the specific players who sustained injuries in a game this season.

I wanted to look into it because I was really interested in what I’ve termed the ‘Jevon Kearse All-Stars.’ It may just be a bad memory on my part, but one of the things I really remember about Jevon Kearse’s tenure with the Eagles was his tendency to hurt himself and fall to the ground like he got shot. I feel like his injuries always looked more serious than they actually were. It’s possible I’m misremembering, and if so I apologize to the Freak. But with that said, here were the league leaders in injury stoppages in the NFL this year:

Now I’m not accusing these guys of faking injuries, these just happened to be the guys with the most injury stoppages in the play-by-play data (excluding special teams, which most of these guys don’t play anyway).

Enjoy your spot on the Kearse All-Stars guys – the trophy (it’s an ace bandage) is in the mail!