CSS Button No Image Css3Menu.com

Baseball Prospectus home
  
  
Click here to log in Click here for forgotten password Click here to subscribe

<< Previous Article
Premium Article What You Need to Know:... (04/29)
<< Previous Column
Baseball Therapy: The ... (04/22)
Next Column >>
Baseball Therapy: Is O... (05/06)
Next Article >>
Premium Article Notes from the Field: ... (04/29)

April 29, 2014

Baseball Therapy

Do Innings Limits Work?

by Russell A. Carleton


Let’s go back to 2012, when the Washington Nationals made one of the most controversial decisions in recent memory by shutting down pitcher Stephen Strasburg late in the season, even though it meant that Strasburg, though not injured at the time, would not pitch for the Nationals in their Division Series. The Nationals lost that series to the St. Louis Cardinals three games to two, and Lana del Rey wrote “Summertime Sadness” as a result (no, not really). The Nationals justified that decision by saying that they wanted to keep Strasburg below 160 innings pitched for the season to prevent him from further injury. In 2011, Strasburg only pitched in five games, spending most of the season recovering from Tommy John surgery. He was healthy through most of 2013 and has been so far through 2014.

Flash forward to 2014, where a laundry list of starters (Jarrod Parker, Patrick Corbin, Jameson Taillon, Kris Medlen, Brandon Beachy, Josh Johnson, and Matt Moore) have already reported to Dr. James Andrews’s office, and we’re not even out of April. Could something have been done to save them? Perhaps the Nationals had it right. Maybe taking it easy with Strasburg in 2012 was the right move.

Today, we’re going to look at the tricky subject of innings limits for pitchers and whether or not they actually “work.” That is, do they show any effect on a pitcher’s health later in his career? But before we jump in, let’s discuss something first. I’m going to be looking at this from a public health perspective. Injury prevention is likely best done with actual X-rays of a pitcher’s elbow and shoulder and a firm understanding of his mechanics and how those mechanics put stress on his joints. But, in the same way that knowing a man is overweight tells me something (but not everything) about his chances for developing heart disease, we can look at innings workloads as an indicator. In the aggregate, do they help or hinder a pitcher’s health? If the answer is yes, then we can at least say that teams should have a bias toward innings limits or not.

Warning! Gory Mathematical Details Ahead!
I gathered stats on the number of innings that pitchers threw, whether in MLB or the minors, from 2000-2013, along with the number of games in which they appeared, the number of batters that they faced, and the number of pitches that they threw. I cross-referenced that with BP’s injury database, which lists both day-to-day injuries for players (when they are reported) as well as trips to the disabled list for that same time period.

For these analyses, I looked only at shoulder and elbow injuries (separately) that required a trip to the disabled list. Because we know that a really good predictor of whether you will suffer an elbow injury this year is whether you suffered one last year, I coded whether the pitcher had experienced an elbow (or shoulder, as the analyses dictated) injury last year or two years ago.

I took all pitchers in their age-23 season who pitched in MLB that year and coded for whether they made a trip to the DL for a shoulder-related issue during that year. That’s a binary outcome (yes/no), so I used a binary logistic regression. I entered as a predictor their previous shoulder injury status, along with their innings pitched stats for their ages 19-22 seasons (again, with inning counts from both the minors and majors)—that is, all data that would have been available up to that point. I also included the total number of cumulative innings pitched up to that point. As expected, last year’s shoulder injury held up as a good predictor of this year’s shoulder injury risk, but innings pitched in the age-22 season also had a significant effect.

The rest of this article is restricted to Baseball Prospectus Subscribers.

Not a subscriber?

Click here for more information on Baseball Prospectus subscriptions or use the buttons to the right to subscribe and get access to the best baseball content on the web.


Cancel anytime.


That's a 33% savings over the monthly price!


That's a 33% savings over the monthly price!

Already a subscriber? Click here and use the blue login bar to log in.

11 comments have been left for this article.

<< Previous Article
Premium Article What You Need to Know:... (04/29)
<< Previous Column
Baseball Therapy: The ... (04/22)
Next Column >>
Baseball Therapy: Is O... (05/06)
Next Article >>
Premium Article Notes from the Field: ... (04/29)

RECENTLY AT BASEBALL PROSPECTUS
The Week in Quotes: November 17-23, 2014
Premium Article Rumor Roundup: If Step One Is Making Betance...
Premium Article The 40-Man Additions
Premium Article The 40-Man Additions
Premium Article Transaction Analysis: The Better Bullpens Bu...
Premium Article Transaction Analysis: Up and Adam
Premium Article 2015 Prospects: St. Louis Cardinals Top 10 P...

MORE FROM APRIL 29, 2014
Premium Article What You Need to Know: Gray Matters
Painting the Black: Singles Falling Steady
Premium Article The Call-Up: Randal Grichuk
Premium Article Minor League Update: Games of Monday, April ...
Fantasy Article The Stash List: Third Edition
Fantasy Article Dynasty Dynamics: NL East U25 Lists
Fantasy Article Closer to Me: Week Five

MORE BY RUSSELL A. CARLETON
2014-05-13 - Baseball Therapy: Analytical Master or Leade...
2014-05-07 - BP Unfiltered: Baseball Prospectus at Fox Sp...
2014-05-06 - Baseball Therapy: Is Oakland's Run Different...
2014-04-29 - Premium Article Baseball Therapy: Do Innings Limits Work?
2014-04-22 - Baseball Therapy: The Houdini Hangover Effec...
2014-04-17 - BP Daily Podcast: Effectively Wild Episode 4...
2014-04-15 - Premium Article Baseball Therapy: Why Sabermetrics Needs Tra...
More...

MORE BASEBALL THERAPY
2014-05-20 - Premium Article Baseball Therapy: Beware the Genius Tag for ...
2014-05-13 - Baseball Therapy: Analytical Master or Leade...
2014-05-06 - Baseball Therapy: Is Oakland's Run Different...
2014-04-29 - Premium Article Baseball Therapy: Do Innings Limits Work?
2014-04-22 - Baseball Therapy: The Houdini Hangover Effec...
2014-04-15 - Premium Article Baseball Therapy: Why Sabermetrics Needs Tra...
2014-04-07 - Premium Article Baseball Therapy: Beware of the Intentional ...
More...