Injury Chances with 10-Day IL (DL)

Injuries analysis is becoming a pain in the butt. First, MLB goes and changes the days missed from 15 to 10 thereby nullifying several projection models. And now they’ve gone and renamed the Disabled List the Injury List. I think of naming it the BDL (Broke D__k List). I’ve been waiting for a few more seasons of DL data to create a new formula which will become obsolete with the 12-day DL but why wait. I have two seasons of 10-day IL information to create a few comparisons, especially for pitchers.

While I’ve historically collected the data, Ryan Brock jumped in and completed the 2018 season. I’m not sure if I would have gotten to pulling it together because when I normally do it (post-season), I was finishing my book. I can’t thank Ryan enough.

In all fairness, most of what follows is a data dump which should be used to help verify or disprove various narratives. I’m not going to make a major claim based on one matched dataset.

Starting Pitchers

For this analysis, I compared data from 2013 to 2016 (3 matched seasons) and 2017 to 2018. I considered a starter to be anyone who started at least 50% of their games in Year 1.

Starting Pitcher Injury Chances
Seasons IL Status Y2 IL% Avg Days Missed Avg # of Trips Count
2013 to 2016 On IL in Y1 49% 51 0.79 383
No IL in Y1 43% 26 0.43 589
% on IL = 39%
2017 to 2018 On IL in Y1 64% 56 1.17 122
No IL in Y1 35% 21 0.48 124
% on IL = 50%

Damn. The separation between the hurt and healthy is more defined with the injured class growing by 11% points (39% to 50%) and with a 64% recidivism rate. Nothing predicts a future injury like a past injury.


These pitchers started less than half their games.

Relief Pitcher Injury Chances
Seasons IL Status Y2 IL% Avg Days Missed Avg # of Trips Count
2013 to 2016 On IL in Y1 33% 35 0.46 300
No IL in Y1 23% 16 0.23 1022
% on IL = 23%
2017 to 2018 On IL in Y1 41% 31 0.61 144
No IL in Y1 30% 17 0.37 342
% on IL = 30%

While the starters diverged into a healthy and hurt class, all the reliever rates went up. It was about 7% point jump in IL time across the board.

Position Players

For simplicity, I just looked at hitters with 1 PA in Year 1.

Position Player Injury Chances
Seasons IL Status Y2 IL% Avg Days Missed Avg # of Trips Count
2013 to 2016 On IL in Y1 35% 26 0.59 557
No IL in Y1 24% 14 0.29 1056
% on IL = 35%
2017 to 2018 On IL in Y1 50% 36 0.92 219
No IL in Y1 25% 9 0.31 406
% on IL = 35%

Like with starters, the shorter IL seems to have created more a divide between the healthy and disabled injured. Well, at least when comparing the two seasons. The previous difference in days missed was just 12 but jumped 27 days. This may be a big deal if the 10-day IL sticks but I just don’t want to too much stock in one dataset.


The 10-day IL may have stratified injury-prone hitters and starting pitchers into two distinct camps. With relievers, they just seem headed to the IL more regularly. We’ll just have to wait to see if these trends continue next season when the dataset doubles in size.


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Jeff, one of the authors of the fantasy baseball guide,The Process, writes for RotoGraphs, The Hardball Times, Rotowire, Baseball America, and BaseballHQ. He has been nominated for two SABR Analytics Research Award for Contemporary Analysis and won it in 2013 in tandem with Bill Petti. He has won three FSWA Awards including on for his MASH series. In his first two seasons in Tout Wars, he's won the H2H league and mixed auction league. Follow him on Twitter @jeffwzimmerman.

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Of course, this is assuming that the players/owners don’t agree to change it back to a 15 day DL. Which is something the players and owners actually do have some agreement on(players proposed 15 days for pitchers/10 for batters).