Too Many Sliders?

“I wouldn’t let a kid at 11-years-old throw a breaking ball, I never threw a breaking ball until I got to high school,” [Tom] Glavine said.

Typically, the rule is that little leaguers shouldn’t be throwing curveballs. The pitch has been blamed for placing too much stress on young elbows, and even a cursory analysis of the mechanics seems to put credence to the credo – it’s a tough pitch to throw. Watching Luke Gregerson throw four sliders out of five pitches to Alex Gonzalez Wednesday night, though, it seemed reasonable to wonder if the slider was also a stressful pitch. Are slider-heavy pitchers more likely to get injured than those that throw the fastball more often?

Let’s look at pitchers since 2008 and set the cutoff rate for slider usage at 40%. Across baseball, pitchers use the slider about 15% of the time, and in our sample of 680 pitchers, only 90 of them failed to use the pitch at least 1% of the time. So nearly 600 pitchers have used the slider regularly in the last three-plus seasons – and only 25 pitchers have used the pitch more than 40% of the time. Those 25 pitchers make up our Slider Group, and naturally Luke Gregerson is included. Michael Wuertz, though, is the king of the hill here. He’s used the slider 64% of the time since 2008, a percentage that usually would be attached to the fastball. Here’s the whole Slider Group, with their fastball and slider velocities and usage rates, as well as a last column with the number of DL trips since 2008.

It should be of little surprise that our Slider Group is mostly relievers – and that the only starter, Jon Lieber, was a reliever in 2008. Throwing the slider 40% of the time doesn’t really allow much space for the third pitch that often separates the starter from the reliever. And it may also not be surprising that their fastballs don’t have the most velocity. Where the average major league fastball clocks in at around 91 or 92 depending on if it’s a four- or two-seamer, these guys have an average velocity of 89.91 on their fastballs. That’s not overwhelmingly slower, but then again, if you had plus-plus velocity on your fastball, you’d probably use it more than your slider, wouldn’t you? So this group uses their fastball 46.3% of the time and their slider… 47.3% of the time!

The group averaged 1.24 trips to the DL over the last three years as a whole, but if you focus only on those that did get injured, they averaged 1.71 trips. Thanks to Jeff Zimmerman, we know that relievers had about a 38% likelihood of hitting the DL over this time period. Since these pitchers didn’t all pitch three years in the sample, we have approximately 64 player-seasons represented. In those 64 player-seasons, we have 31 trips to the DL, or a 48.4% likelihood of hitting the DL.

In this sample of 25 players over the past three years, we have have ten surgeries and a major Rotator Cuff injury. Bill Bray, Pat Neshek, Dan Giese and Mike Gonzalez all had Tommy John surgery, a 16% rate that is already far ahead of the major league rate for all pitchers. USAToday reported in 2003 that 75 of 700 major league pitchers had undergone the surgery (10.7%), and since Jon Lieber is also a TJ survivor, 20% of this group has had the surgery. If you zoom out on this group’s careers, you add seven more surgeries and another major Rotator Cuff injury, meaning that this selection of 25 pitchers has endured 17 surgeries and two major Rotator Cuff injuries as a whole over their careers.

Every pitcher is different. We can’t use this work to say that Carlos Marmol is inevitably headed for surgery in the coming years. This is not a comprehensive study, and we cannot make an equation of the results. 40+% slider usage does not equal Tommy John surgery. But it certainly doesn’t look like throwing the slider that often puts you in healthy company.