10 Year Disabled List Trends

With disabled list information available going back 10 years, I have decided to examine some league wide and team trends.

League Trends

To begin with, here are the league values for trips, days and average days lost to the DL over the past 10 years.

Generally the data shows that days lost and trips generally go up to a peak near 2007 to 2009 and then drop down a bit in the last couple of years. The most recent issue of ESPN the Magazine states:

“But industry experts have noticed that the window of lower rates [in the early 2000’s] could mark the peak of performance-enhancing drugs, which are thought to accelerate recovery.”

While the article may suggest that PEDs were behind the spike, I would like to bring forth another cause. The age of the players. Here is a graph of the average age of hitters and pitchers since 2002:

Hitters have, on average, got 0.5 years younger while the average pitcher’s age went up 0.5 years and then dropped 0.7 years. The increase and then drop in days lost may have more to do with younger, less injury prone players in the league than PEDs. To show the point further, here is a graph of the average age of pitchers and hitters over the 10 years versus the days lost to the DL.

While I am dealing with a small sample size, there is a decent correlation (R-squared of 0.51) between average days lost to the DL for pitchers and their average age.

Team Data

Here is the cumulative values for Days and Trips to the DL over the past 10 years.

The main point when looking at the long term trends is how the Chicago White Sox are able to lose fewer than half the number of days as 8 other teams (Colorado, Arizona, Kansas City, Cincinnati, LA Dodgers, Washington, New York Mets and Texas). In the last few years some teams, like the Dodgers, have tried to put a better foot forward in limiting injuries.

Another point is that teams have an expected winning percentage as seen in this discussion at The Book Blog. Some teams under and over perform their expected winning percentage based on the team’s salary over the last 10 years. Some of the teams who under performed, like the Mets and Royals, are at the top of the days lost to the DL. Teams who have out performed their expected winning percentage, like the Cardinals and Twins, are in the bottom half of the list. It takes money to get wins in baseball. If that money is sitting on the bench because of an injury, the team can just expect to win fewer games.

For more recent trends, here is a look at the days lost to the DL over the last 10, 3 and 1 year intervals.

Some teams, like the Royals, Rangers and Cubs, have seen marketed improvements in the last few years. Other teams like the Dodgers, who are supposed to be on the tip of the spear in disable list prevention, are only seeing their numbers get worse.

Finally enough data is available to make some OK conclusions from disabled list data. The time lost to players on the DL peaked a few years ago, but has been heading down because of possible decreases in PED use and/or the declining ages of players in the league. Some teams are beginning to put forth more of an effort into prevent DL trips. The results right now look mixed. Team will never be able to prevent all injuries, but they can aim to prevent as many as possible.