Injury Chances for Strike-Throwers

In the Oct. 15 issue of ESPN the Magazine, Tim Kurkjian wrote this when talking about young pitchers with injury histories:

GM Billy Beane doesn’t require power, he wants outs without walks. Plus strike throwers generally have good mechanics that help prevent injury. Beane also isn’t afraid to go with young pitchers, what at least in theory are less likely than older ones to get injured.

The line that caught my interest is the one that “strike throwers generally have good mechanics that help prevent injury.” I will try to see if any truth exists in that statement.

Immediately, I spotted three chicken-and-egg scenarios that include mechanics, strike throwing and injuries:

Scenario No. 1: Good mechanics equal More strikes and less injuries

Scenario #2: No injuries equal good mechanics and more strikes

Scenario #3: More strikes equal good results, which equal less of a chance of a fake injury.

I think the truth is a combination of all three. I am not going to get into what may be the possibly cause of what. I just want to see if “strike throwers” are less injury prone. It is tough to know if a statement may be true or not until the numbers are run.

I looked for strike throwers using three stats available at FanGraphs, percent of strikes thrown (Strikes/Pitches or Strike%), Zone% (Pitchf/x *) and non-intentional walk rate (NIBB). I had no idea how a pitcher gets labeled a “strike thrower,” but those three stats seemed like a good place to start. To get a base sample of pitchers, I looked at starting pitchers who threw at least 120 innings in one season and then how many of those ended up on the DL the next season. Historically, 41% of these pitchers end up on the disabled list the next season. After rerunning the numbers for this study, the percent chance of a DL trip has gone down to the 37%-to-39% level.

I divided up the three categories into three ranges with a similar number of samples in each grouping to get the percentage of pitchers who ended up on the DL.

% Strikes DL%
>64% 38.3%
62% to 64% 36.5%
<62% 36.3%
Zone% DL%
>51.5% 34.5%
51.5% to 49% 41.2%
<49% 41.4%
<6.5% 36.3%
6.5% to 8% 35.2%
>8% 39.6%

Average values:37% for Strike% and NIBB%, 39% for Zone% (Pitchf/x values)

The only number that sticks out is the >51.5% value for Zone%. I further divided that group of pitchers up and couldn’t find that the DL% decreased any more. I found that the percent of pitchers who went on the DL was 35.3% for a >51% Zone%. I will use the 51% value because it will be an easier number to remember. In 2012, 35 pitchers ** met this criteria of being a possibly healthy pitcher.

While I was only able to find one of the three categories that showed strike-throwers being healthy, I did find that extreme non-strike throwers had a higher likelihood of ending up on the disabled list.

% Strikes DL%
< 60% 45.0%
Zone% DL%
< 47% 49.0%
>10% 49.2%

A Zone % less than 47%, or a NIBB% more than 10%, puts the pitcher in a 50-50 chance of ending up on the DL. While the Strike% value is not near 50%, it still shows a higher injury chance.

For an example, seven pitchers from 2007 to 2011, met all three of the above requirements in a single season.

Name Season IP age Strike% Zone% NIBB% D.L.
Carlos Zambrano 2010 129.2 29 59.1% 46.6% 12.1% Yes
Doug Davis 2007 192.2 32 58.6% 46.5% 10.2% Yes
Daniel Cabrera 2007 204.1 26 58.1% 44.9% 11.1% Yes
Francisco Liriano 2011 134.1 28 57.2% 43.5% 12.5% No
Roberto Hernandez 2009 125.1 29 59.4% 46.4% 11.7% No
Kyle Davies 2009 123.0 26 58.0% 44.2% 12.1% No
Yovani Gallardo 2009 185.2 23 59.2% 45.7% 11.2% Yes

Four of the seven ended up on the DL the next season. Two pitchers in 2012 met all three criteria: Edinson Volquez and Ricky Romero. It seems more than likely one or the other will be sidelined in 2013. Including Volquez and Romero, here is a table of the 25 pitchers who have a high chance of ending up on the DL in 2012 because they couldn’t throw strikes.

Name Season IP age Strike% Zone% NIBB% # of Instances
Edinson Volquez 2012 182.2 29 59.8% 45.7% 12.3% 3
Ricky Romero 2012 181 28 59.0% 46.2% 12.6% 3
Tim Lincecum 2012 186 28 61.2% 45.2% 10.6% 2
Yovani Gallardo 2012 204 26 59.8% 45.2% 9.1% 2
Carlos Zambrano 2012 132.1 31 58.9% 47.4% 12.5% 2
Ubaldo Jimenez 2012 176.2 28 58.8% 48.6% 11.4% 2
Jeremy Hellickson 2012 177 25 62.6% 43.4% 7.6% 1
Luis Mendoza 2012 166 29 60.2% 43.5% 7.9% 1
Josh Johnson 2012 191.1 28 61.6% 44.4% 7.3% 1
Trevor Cahill 2012 200 24 60.8% 44.4% 8.8% 1
Edwin Jackson 2012 189.2 29 62.8% 44.6% 6.7% 1
James Shields 2012 227.2 31 64.3% 44.9% 5.9% 1
Jon Lester 2012 205.1 28 62.2% 45.0% 7.5% 1
Jake Westbrook 2012 174.2 35 63.3% 45.8% 6.9% 1
Shaun Marcum 2012 124 31 63.4% 45.9% 7.4% 1
Stephen Strasburg 2012 159.1 24 63.2% 46.2% 7.2% 1
Jarrod Parker 2012 181.1 24 61.7% 46.3% 8.0% 1
Hiroki Kuroda 2012 219.2 37 62.9% 46.6% 5.5% 1
Jerome Williams 2012 137.2 31 63.5% 46.6% 5.9% 1
Gio Gonzalez 2012 199.1 27 62.0% 46.6% 8.9% 1
Tommy Hanson 2012 174.2 26 62.1% 46.6% 8.7% 1
Yu Darvish 2012 191.1 26 62.3% 47.7% 10.8% 1
Felix Doubront 2012 161 25 62.6% 48.1% 10.0% 1
Matt Moore 2012 177.1 23 63.1% 50.0% 10.0% 1
C.J. Wilson 2012 202.1 32 60.8% 50.7% 10.3% 1

Some big names fill the list, including free agents Edwin Jackson and Hiroki Kuroda.

Gio Gonzalez is an interesting name here, too. In 2011, he had a 59.9% Strike%, 47.3% Zone% and 10.4% BB%. Two of the categories are within the higher injury threshold and one is almost included in it. I am wondering if this was one of the reason Billy Beane traded Gonzalez after the 2011 season to the Washington Nationals.

Some merit does exist from the statement “strike throwers generally have good mechanics that help prevent injury.” Using the a pitcher’s Zone% value (Pitchf/x), some pitchers can be marked for having a less-than-average chance of ending up on the DL. The main fact is that pitchers at the far end of the non-strike-throwing spectrum are more likely to get hurt. These pitchers, who have problems getting the ball over the plate, have a near 50% chance of ending up on the disabled list the next year. Pinpointing exactly who will end up injured is impossible, but some idea of increased chances can be measured. Also Billy Beane is right, again.


* I wanted to use the BIS Zone% values, but the values weren’t consistent enough over the years. Initially, I found 48% of the pitchers with a Zone% less than 45% went on the DL. Then, I looked to see the number of pitchers who would be on the list for 2012. Sixty-three of the 107 possible pitchers made the list. I went back and ran the numbers for each year and got:

2012: 63 of 107
2011: 75 of 124
2010: 54 of 120
2009: 11 of 102
2008: 0 of 111
2007: 10 of 114
2006: 1 of 104
2005: 0 of 122

I found the data were useless.

Using the PITCHf/x zone I ended up with the following values each year:

2012: 18 of 107
2011: 18 of 124
2010: 14 of 120
2009: 14 of 102
2008: 10 of 111
2007: 22 of 114

These values were more consistent and made more sense.

** Kevin Millwood, Erik Bedard, Blake Beavan, Bartolo Colon, A.J. Burnett, Kyle Lohse, Bruce Chen, Bronson Arroyo, Tommy Hunter, R.A. Dickey, Cliff Lee, Chris Capuano, Kevin Correia, Justin Masterson, Ross Detwiler, Zach McAllister, Max Scherzer, David Price, Clayton Richard, Ricky Nolasco, Derek Holland, Jon Niese, Jordan Zimmermann, Madison BumgarnerMatt Harrison, Henderson AlvarezIan Kennedy, Phil Hughes, Justin Verlander, Brandon Morrow, Kris Medlen, Doug Fister, Travis Wood, Chris Sale, Wei-Yin Chen

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Jeff writes for FanGraphs, The Hardball Times and Royals Review, as well as his own website, Baseball Heat Maps with his brother Darrell. In tandem with Bill Petti, he won the 2013 SABR Analytics Research Award for Contemporary Analysis. Follow him on Twitter @jeffwzimmerman.

18 Responses to “Injury Chances for Strike-Throwers”

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  1. MGL says:


    As you correctly mention, there are all kinds of selective sampling and cause/effect issues that confound an analysis of this data.

    To me, the most salient one is this: Certainly some not insignificant percentage of pitchers who threw fewer strikes (had control problems) already had some sort of injury and were just a DL trip waiting to happen.

    If that is true then it is sort of in opposition to Kurkjian’s “theory.” I say sort of because it might also be true that when a pitcher is injured but still pitching, his mechanics are altered or are more inconsistent, causing control problems.

    The thing I object to, at least without evidence (I’m not saying that it’s not true) is the “common sense” notion that if you have “poor” mechanics, you are more likely to get injured. While “poor” mechanics, by definition, might limit your ability to be a good pitcher (by limiting control, command, and velocity), there is no particular reason that I can think of that it also increases your chances of being injured. In fact, I can come up with a “common sense” argument that poor mechanics can preserve health by not allowing the body to stress itself as much.

    I think an interesting thing to look at is pitchers who have a change in their strike throwing ability and see how that relates to their chances of being injured.

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    • Jeff Zimmerman says:
      FanGraphs Supporting Member

      Give me a week or two. I am getting closer to publishing a look at injuries an a game by game level. Data is a little bit of a mess is the main hold up.

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  2. DTF_in_DTL says:

    There seems to be a correlation between “clean” repeatable mechanics and being able to throw strikes when you want to. It also seems command goes first, then velocity due to injuries. How about adding in how reliable / consistent their release point and velocity are. Maybe even across pitch types if possible. You may even be able to model when a pitcher is getting “injured” as their %zone goes down (loss of control), babip goes up (loss of command), and release point becomes inconsistent (loss of repeatable mechanics).

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  3. Robin says:

    I’d be interested to know if throwing more breaking balls leads to both throwing less strikes and being more likely to be injured. It stans out as possibly another variable that we might want to take into account.

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  4. Matt Hunter says:
    FanGraphs Supporting Member

    Another common thought is that tall pitchers have harder time creating clean, repeatable, mechanics, and therefore have control issues. I wonder if height has anything to do with this (I doubt it, but it’s possible).

    Here are the heights of the pitchers in that short list:

    Zambrano: 6′ 5”
    Davis: 6′ 4”
    Cabrera: 6′ 9”
    Liriano: 6′ 2”
    Hernandez: 6′ 4”
    Davies: 6′ 1”
    Gallardo: 6′ 2”

    Most of these guys are above average height (I believe average is 6′ 2” or so), and the guys that got injured are the taller ones of the group. Of course, this is a laughably small sample size, and means nothing. Still, would be interesting to look into.

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    • brendan says:

      MLB pitchers (and pos players!) in general are taller than avg. I don’t think this group is particularly tall by MLB standards.

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      • Matt Hunter says:
        FanGraphs Supporting Member

        Right, by average I meant average for MLB pitchers. According to Kevin Goldstein here, average pitcher height is 6′ 2”. The average height of the guys above is just under 6′ 4”. Of the 4 injured guys it’s 6′ 5” and of the 3 non-injured guys it’s just over 6′ 2”. But like I said, too small of a sample to say anything meaningful.

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  5. Are you even serious? says:

    Talk to bio-mechanic experts. Control does not equal efficiency. Not even close. Prime example: Kevin Slowey. Terrific control, tons of DL time. He has simple, repeatable, easy mechanics. Yet his follow through (which is not correlated with control) where he lacks optimal pronation after release causing injury.

    Also, obvious factors include strength, flexibility and mobility, etc. I think strike throwing and/or repeatable deliveries typically come from those with efficient mechanics. But a bio-mechanical anaylsis is the independent variable affecting the other two dependent variables.

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    • Ben Hall says:
      FanGraphs Supporting Member

      This is bizarre. Are you actually suggesting that Jeff’s large sample that supports the idea is nullified by your one example?

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  6. Kyle Boddy says:

    Interesting case study!

    Aside from the comments mgl pointed out, have you done more rigorous statistical analysis on the data to see how likely these effects are occurring compared to random chance? (t-test, regression, etc)

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  7. Nathaniel Dawson says:

    Yeah, I don’t know. I look at the data you present and it looks to me like more noise than any kind of indication of anything. The numbers are all very close, and seem to be somewhat contradictory when looking at the “strike-oriented” metrics. The one result you singled out as most interesting isn’t that far off from the norm. ~38% of all pitchers in the study hit the DL the next season, while only 34.5% of the high zone% did so. You chose equal numbers in each group, so the “others” hit the DL at a 41% rate. Or, the difference between that group and the others is about one in eighteen pitchers. Maybe that has some significance, and is worth looking into further, but there’s nothing from what I see to corroborate or confirm anything. To me, it looks likely to be randomness more than any particular pattern.

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  8. Patrick says:

    Nice write-up. Definitely adds some clarity, but I agree more granularity is needed before we make an absolute conclusion (which may never happen :))

    First, I agree mechanics can be a major factor in reducing or eliminating injuries. Its clear from watching the likes of Andy Pettitt that having a clean repeatable delivery can keep one healthy and effective over a long time. That being said so many other things go into being able to do that-that we may become overloaded with data and start assuming all sorts of biases.

    Ultimately, we should also account for TYPE of injury. It would be incorrect to assume that poor mechanics would lead to something as freakish as a hip injury incurred when running the bases (Chen Ming Wang) vs. someone blowing out their elbow multiple times as a result of overthrowing (Zumaya). I dont know if that was accounted for here. The same would go for liners back to pitchers that cause injury and perhaps other types of injuries that may be construed as not mechanics related.

    The last point here is that it may be incorrect on Beane’s part to assume young pitchers have a lower chance of injury than older pitchers. I would use opposite logic to posit that older pitchers have a better chance of surviving injury for the following reasons:

    *I have no data to back these up……

    1: Older pitchers probably do not overthrow or rely on “Stuff” to get guys out, but rather are more capable of using the strike zone to get guys to chase.

    2. Can get out of jams better by not giving in, thus limiting pitch counts.

    2: Are already older pitchers, thus having already established themselves as reliable pitchers, thus meaning less time on DL. What I mean is, a pitcher who spends time on the DL probably doesnt last as long as someone who doesnt spend time on the DL, so being an older pitcher, one would assume they didnt spend a lot of time on the DL….right?

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  9. vivaelpujols says:

    Something I noticed was that pitchers who threw more *strikes* actually had a slightly higher DL% than average while pitchers who had a higher Zone% had a lower chance of injury.

    I think what you’re seeing here is that pitchers with better stuff have more out of zone strikes and are more likely to be injured than pitchers throw an equal amount of in zone strikes but fewer out of zone strikes.

    So I guess Beane’s theory holds up, but I’m also guessing that injury rate is positively correlated with a high K rate, which is probably the best indicator of performance.

    Jeff, how does strikeout rate in year n project injury rate in n+1?

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    • Jeff Zimmerman says:
      FanGraphs Supporting Member

      Viva – I just ran the numbers. and there is some signs that show high K pitchers are a bit more injury prone.
      K%: DL%
      >21%: 39%
      18% to 21%: 41%
      14% to 18%: 36%
      12% to 14%: 32%
      < 12%: 34% I really like the Pitchf/x Zone% for looking at the values.

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  10. rgathman1115 says:

    A multitude of variables come in to play when you talk about the reason for a DL visit. Personal fitness and strength, lifestyle and diet habits, lifetime pitch/throw counts, throwing mechanics, freak injuries and many more. Due to the countless variables that can’t be quantified it is very tough to say that any logical relation can be made between throwing strikes and DL visits.
    What I believe Beane is indicating is that he prefers pitchers that focus on executing pitches and working the zone instead of pitchers that try to light up the radar gun, or overthrow. Overthrowing can certainly lead to increased injuries due to added stress on the body.
    Consider pitchers in the early 20th century that would throw both games of a double header with a pitch count reaching the 300s. Their style was focused on location over velocity, with a heavy reliance of defense. Those pitchers lasted because they weren’t maxing effort out on every pitch. Fireballers today, that Beane tries to avoid, seem to try to throw maximum velocity from pitch 1 to pitch 100. That maximum effort in every pitch is going to add an undeniable strain that a “strike thrower” wouldn’t face when focusing on location over velocity. To randomly quantify that logic, a fireballer is throwing roughly 1.1 pitches to every 1.0 pitches a “strike thrower” throws. At the end of a game both pitchers throw 100 pitches, but with the added stress a fireballer endures after max effort on every pitch, it is as if he has thrown 110 pitches. Now, these numbers obivously have no real statistical backup, they are used simply to help illustrate my point.
    Also a statement Kurkjian made that interested me was “younger players, in theory, are less likely to get injured than older players”. Is there any statistical validity to this statement?

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