Curveball and Slider Pitchers and the DL
Recently, I posted my 2012 starting pitcher DL projections. In the projections, I used games started, age, and injury history to predict the percentage chance a pitcher will end up on the DL. Today, I am going to give an initial stab at how throwing a large number of curveballs and sliders affects a pitcher’s DL chances.
I started by looking at the season after the season in which a pitcher threw over 120 innings. Normally, 39% of these pitchers will end up on the DL. The percentage increases even more if the pitcher threw a large number of sliders or curveballs.
I wanted to look at extreme slider pitchers. For the cutoff, I used pitchers who threw sliders over 30% of the time. For this list, we found 43 pitcher seasons (around four pitchers per year). The list includes such names as Francisco Liriano, Hiroki Kuroda and Ervin Santana.
The list is not huge. Most starters limit the number of breaking balls they throw. On the other, of the qualified relievers in the league, around 14 pitchers per year make the 30% threshold in one of the breaking ball categories. The problem right now with looking at relievers is that we haven’t established a baseline DL percentage. For now, I will have to work with the limited number of starters. Of these pitchers, over 46% of them ended up on the DL in the next season. While that isn’t a huge jump, it does show some of the extra stress that throwing sliders puts on a pitcher’s arm. To get an idea of pitchers who threw a large number of sliders, here are the top 10 slider-throwing starting pitchers from 2011.
| Rank | Name | SL% |
| 1 | Ervin Santana | 38.4% |
| 2 | Bud Norris | 36.2% |
| 3 | Edwin Jackson | 33.7% |
| 4 | Madison Bumgarner | 32.4% |
| 5 | Michael Pineda | 31.5% |
| 6 | Ryan Dempster | 31.1% |
| 7 | Francisco Liriano | 28.8% |
| 8 | Bruce Chen | 28.7% |
| 9 | Felipe Paulino | 28.3% |
| 10 | Alexi Ogando | 27.7% |
For curveballs, I have to move the percentage minimum down even lower (to 25%) to get a decent number of pitchers. Twenty-seven pitcher seasons make that threshold, with such names as A.J. Burnett, Josh Beckett and John Lackey populating the list. Of these starter seasons, 51% of the pitchers ended up on the DL the next season. For reference, here are the top 10 curveball-throwing starters from the 2011 season:
| Rank | Name | CB% |
| 1 | Wandy Rodriguez | 37.2% |
| 2 | A.J. Burnett | 33.1% |
| 3 | Erik Bedard | 31.2% |
| 4 | Gio Gonzalez | 27.8% |
| 5 | Jeff Niemann | 23.7% |
| 6 | Jonathon Niese | 22.9% |
| 7 | Brett Myers | 22.7% |
| 8 | Ivan Nova | 22.4% |
| 9 | Philip Humber | 21.7% |
| 10 | James Shields | 21.0% |
These pitchers have some added risk for missing time in the season. The risk must be weighed with the pitcher’s quality and age to determine their value. If you are looking at two pitchers that have similar projected numbers, look to pick up the pitcher who throws fewer sliders or curveballs.
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 four FSWA Awards including on for his Mining the News series. He's won Tout Wars three times, LABR twice, and got his first NFBC Main Event win in 2021. Follow him on Twitter @jeffwzimmerman.
Not a statistician myself, but is there a way to control this data for age?
I did a bit, but I was limited on the sample size even more. Their was a gap with the sliders throws and not with curveballs.
The more I look at the data, the more I need to get a baseline with RP and then look at them.