Note: Pitch data (type and velocity) from Baseball Info Solutions dating back through the 2002 season is available at FanGraphs. This post utilizes that data, not the automatically generated numbers from Pitch f/x.
Thursday of last week, Al Alburquerque, the surprising rookie sensation whose electric slider provided a spark out of the Detroit Tigers’ bullpen this year, underwent surgery to correct a stress fracture in his valuable right elbow.
In July, Jordan Gorosh wrote on this site that Alburquerque, as any other pitcher who uses a slider as a primary pitch, was “a ticking time bomb.” Quite right. To back up his stance, Gorosh linked to a post on FanGraphs that showed the correlation between a high slider selection rate and trips to the disabled list. The article looked at a sample, the “Slider Group” as it was termed by author Eno Sarris, which included 25 pitchers, who, over the course of three seasons between 2008 and 2010, used their slider at least 40% of the time. The 25 pitchers in the Slider Group made a total of 31 DL trips in those three years, and only eight of them were never placed on the DL during that span.
I wanted to accentuate the idea outlined in the FanGraphs piece with some research of my own. To accomplish this, I expanded the sample and looked at things from an alternate perspective, using differences from year to year in innings pitched totals rather than counting DL trips to gauge the wear placed on arms due to exorbitant slider usage.
As noted at the top of this post, I used the data available on FanGraphs and gathered by Baseball Info Solutions to gather 86 pitcher seasons (from 2002-2010) in which a pitcher threw more than 40% of his pitches for sliders and did so over at least 40 innings at the major league level. Those 86 seasons were posted by 54 different players. Jamie Walker, Bobby Seay, and Casey Fossum each made the list as Tigers in 2002, 2007, and 2008 respectively.
For the 83 pitcher seasons left, we have a total of about 5,328 innings pitched, which works out to an average of around 64 IP/season. Now, the interesting part: the pitchers who put up the seasons in the sample followed those seasons up by pitching a total of around 3,942 innings at the major league level the next season, an average of about 47 IP/season.
To recapitulate, pitchers who throw at least 40% sliders in a season over at least 40 innings throw an average of 17 fewer innings the following season; that’s a 26.6% decrease. Further, only 24 pitchers increased their workload the year after throwing enough sliders to be included in this sample.
Note that, because I lack both time and a staff of interns to work on my spreadsheets, this study does not include innings pitched in the minor leagues. Even if those minor league innings were added, though, it wouldn’t come close to making up the difference in innings pitched from year to year.
No matter how you look at it, it’s apparent that guys who rely on sliders are much more susceptible to injury than your average pitcher.
Next year, guys to keep an eye on, besides Alburquerque, who figures to return shortly after the All-Star break, include Carlos Marmol, Rafael Perez, Luke Gregerson, Sergio Romo, Jesse Crain, Louis Coleman, Todd Coffey, Michael Stutes, and Will Ohman, all of whom relied heavily on their sliders in 2011.
For the full spreadsheet listing slider selection rates, pitch velocity, pitch value, and innings pitched differences for every pitcher season in this sample, click here.