Football is a game of attrition, and every team must deal with injuries over the course of a season. But you need some extra bad mojo to get hit the way the Cowboys got hit with injuries last year.
Every year, Football Outsiders publish their statistical study of team health from the previous NFL season. For 2020, FO determined that the Cowboys were one of the teams hardest hit by the injury bug, at least according to their metric called Adjusted Games Lost (AGL). In their own words:
... adjusted games lost aims to measure the impact of injuries on teams. As you likely intuit, a starting offensive tackle matters more to his team than a special teams player. Adjusted games lost captures that distinction with separate weightings of starters, replacement starters, situational players, and bench players. In addition, the metric adjusts the weightings of active players who appeared on their teams’ injury reports prior to playing to account for an anticipated decrease in effectiveness while playing hurt.
By FO’s definition, the Cowboys finished the 2020 season with 118.5 Adjusted Games Lost. Ranking teams from the healthiest (#1 Tampa Bay with 30.6 AGL) to the most injured (#32 San Francisco, 166.6 AGL), the Cowboys ranked 28th last year. Just a year before, the Cowboys had been a paragon of health, ranking fourth overall in terms of AGL. The following table shows where the Cowboys have ranked over the years in terms of AGL.
|Dallas Cowboys' Rank in Adjusted Games Lost to Injury, 2008-2020|
On balance, the Cowboys have enjoyed positive injury luck over the last 12 years: in five of the last 12 seasons (marked in green) they were among the least-injured teams in the league, five years (no color) saw them with a league-average AGL, and two seasons (red) saw them at the bottom of the league in terms of AGL.
But 2020 proved to be a double whammy for the Cowboys. Not only did they have a high AGL rate, those AGL proved to be highly concentrated.
Their [bottom-five] overall total of adjusted games lost was concentrated on offense, and more specifically the quarterback and line that represented the anticipated strength of their team.
Dak Prescott was sixth in passing DVOA in 2019 and eighth in 2020 before his ankle injury. Meanwhile, Tyron Smith, Zack Martin, La’el Collins, Cameron Erving, and Joe Looney all missed time on the offensive line. Smith and Martin have 12 Pro Bowl berths and six first-team All-Pro distinctions between them, and so it was little surprise to see the Cowboys decline from second in both adjusted line yards and adjusted sack rate in 2019 to 12th and 14th in those metrics last year.
The image below highlights the highly asymmetric injury distribution on offense in 2020:
The 2020 Cowboys offense was ranked 29th in the league with 75.6 Adjusted Games Lost. The defense on the other hand, despite injuries at linebacker (Leighton Vander Esch, Sean Lee) and cornerback (Chidobe Awuzie, Anthony Brown, Trevon Diggs) ranked a middling 18th in the league with 42.8 Adjusted Games lost.
Statistically speaking, there are two main reasons for optimism in the numbers presented above, “regression toward the mean” and “normal distribution”.
Regression toward the mean
This statistical phenomenon describes the fact that if a variable is extreme on its first measurement, it will tend to be closer to the average on a second measurement. In our case today, it means that teams with a very high injury rate one year tend to have a better injury situation in the following year, while teams with an extremely low injury rate tend to have more injuries the following year.
Specifically, it’s very likely that the Cowboys offense will see a lot less injuries in 2021. This is a good thing, and even Football Outsiders picked up on this fact.
On the whole, the playoffs were full of healthy teams. Seven of the top 10 teams in adjusted games lost reached the postseason, and only Washington won their division while finishing in the bottom third.
That trend should likely inform the Falcons’ (48.0 adjusted games lost, third) and Texans’ (58.2, seventh) decisions to either try to compete immediately or rebuild. They have little room to improve in the injury department, which means the whole of their gains must come from improved play.
In contrast, teams such as the Chargers (109.1, 27th) and Cowboys (118.5, 28th) may already have contenders and just need a bit better luck to realize that potential.
We know that injuries are a fact of life in the NFL. We also know that a good amount of injuries suffered are random: the healthiest team in 2019 (MIN: 25.6 AGL) dropped back into the middle of the pile and ranked 16th last year (83.5 AGL); the Cowboys ranked 4th in 2019 and dropped all the way to 28th in 2020. These types of swings happen every year, but they are the outliers. Most teams will oscillate to various degrees around the league average, and that’s a reasonable expectation for the Cowboys in 2021. And that little bit of extra health may be all the team needs to take the NFC East.
Without going into discussions about bell curves and standard deviations, a normal distribution in statistics holds that the most common values are near the mean and the less common values are progressively farther away from it.
In the simplest possible terms for the Cowboys: The Cowboys should expect a better distribution of the injuries across the entire roster, which in turn should make the impact of those injuries less crippling.
You saw in the image of the starting offensive lineup above that the O-line starters missed a combined 39 games. Add injuries to some of the backups and you have an AGL total of 46.4, which ranked the Cowboys 31st in the league. Expect that value to come down as injuries are more evenly distributed across the entire roster.
Unfortunately, while that normal distribution should be good news for positions like QB, TE, and OL that were hit particularly hard by injuries last year, it’s bad news for the WR and RB room: The Cowboys had the lowest AGL in the league at wide receiver and the third-lowest AGL at RB. Don’t expect a repeat of that this year.
Overall, it’s quite reasonable to expect the Cowboys to have better injury luck this year. Will it be enough to make the playoffs?
I don’t know, but I think it will be.
And our old friend rabblerousr agrees: