Stress, Strain, and the MLB Disabled List

One of the things we do at Sportavida is use physiologically relevant measures to detect stress and fatigue. By making measurements that matter a baseball player may be able to avoid overuse problems and avoid the disabled list.

Is overuse a problem in baseball?

The simple answer is that the disabled list (DL) costs teams plenty. Taken in aggregate, the DL in 2016 cost teams more than $670 million in lost player investment . Cost of lost player investment was calculated as the pro-rated salary of the time the injured player was inactive, with the cost of the replacement player on the active 25-man roster subtracted from that cost, for a net loss to the team. However, the simple numbers themselves don’t give a direct answer so we did some analysis.

There were 571 incidents of a player going on the DL in 2016. 120 of these placements were at the start of the season. For the purpose of this analysis we removed these data from subsequent analysis since being on the DL at the start of the season had nothing to do with play during the 2016 season and thus incidents were not related to overuse (at least in 2016). This leaves us with a total of 451 DL placements.

First, we wanted to know if there were any difference between players with regard to chance of going on the DL. Big differences between positions might tell us who really might be having problems with overuse and who really should be monitored very closely. The following table shows that pitchers are far more likely to go on the DL than other players. This is not a big surprise but it is stunning to see just how lopsided these numbers really are.

Position count Percent
RHP 183 40.6
LHP 52 11.5
LF 41 9.1
C 35 7.8
RF 31 6.9
CF 28 6.2
2B 22 4.9
3B 21 4.7
SS 19 4.2
1B 16 3.5
DH 3 0.7
Total 451 100

Next, we looked to see if teams are really different. If occurrence is really different then maybe going on the DL means something different from one team to another. The answer here is mixed. Differences between teams are not statistically significantly different (0.082 Pearson Chi-Square) but some variation is noted. The Angels, Dodgers, Athletics, Braves, and Giants all had more than 20 (23 highest) guys go onto the DL whereas the Phillies, Brewers, and Astros all had less than 10 (6 lowest). The conclusion here is that teams are pretty much equally afflicted though there are some differences.

Overuse is the main reason for getting on the disabled list

We can say that DL placements happen more in pitchers and teams are more or less the same in terms of rates of the DL. However, our big interest is determining if the reason for going onto the DL is really related to overuse. To answer this question, we looked at the stated reasons player get on the DL. During 2016 no less than 76 different reasons were given. However, the list is pretty lopsided and most reasons only have a single player associated with a stated reason. The following table contains the reasons for which there are four or more reported instances.

Reason Count Percent
strain 130 28.89
inflammation 44 9.78
strained 42 9.33
tendinitis 19 4.22
sprain 18 4.00
injury 14 3.11
sprained 13 2.89
fractured 12 2.67
fracture 11 2.44
contusion 10 2.22
impingement 10 2.22
discomfort 9 2.00
tightness 9 2.00
concussion 8 1.78
soreness 8 1.78
blister 6 1.33
broken 4 0.89
fatigue 4 0.89
irritation 4 0.89
The total of these top 19 reasons make up 269 or 83.3% of the DL explanations. Some of these reasons indicate overuse while other are related to trauma. The overuse reasons are: strain, inflammation, strained, tendinitis, discomfort, tightness, soreness, fatigue and irritation (indicated in red). These overuse categories make up a whopping 59.8% of DL placements during the season. Yes, overuse is a BIG issue for sure.

Next, we asked if overuse reasons were occurring more frequently in some types of players relative to others. We addressed this by comparing the rates of overuse reasons to incidence of going on the DL. This result is shown in the following table.

Position All Overuse Diff.
RHP 40.58 47.96 7.38
LHP 11.53 12.64 1.11
LF 9.09 8.92 -0.17
C 7.76 7.43 -0.33
RF 6.87 6.69 -0.18
2B 6.21 4.09 -2.12
3B 4.88 4.09 -0.79
CF 4.66 3.35 -1.31
1B 4.21 2.60 -1.61
SS 3.55 1.86 -1.69
DH 0.67 0.37 -0.29
Total 100.00 100.00 0.00
The table shows that overuse reasons occur more frequently in right-handed pitchers than any other position group.

Taken together an examination of the 2016 DL data shows that overuse is a big problem and account for 59.8% of all reasons why players go on the DL during the season. The economic impact is conservatively estimated at about $400 million per year.

We think that overuse can be avoided with careful monitoring of relevant physiological processes. This will save teams money. Also, a healthier team is going to be a winning team over the long season.

The source data are available at MLB DL Data

By |2017-07-15T19:22:17+00:00January 30th, 2017|Baseball|0 Comments

Leave A Comment

three + 11 =