FanGraphs Baseball


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  1. Has anyone ever looked at curve ball velocities and ever found anything suggestive of anything? (slower curve balls break more and hence are more effective; faster curveballs break sharper and hence are more effective; curve ball velocity or perhaps use fluctuates over time and correlates in such-and-such a way with effectiveness; and so on)

    Comment by Richie — April 30, 2012 @ 11:12 am

  2. My understanding of these curves remains that they’re underestimating the impacts of age. If I have two 34-year old pitchers, but next year one retires and the other continues to pitch, it’s pretty likely the one that retired ‘decayed’ more than the one who still throws, e.g he no longer has a job because his fastball slipped to 86 instead of 88 over the offseason. But the guy who now throws 86 isn’t observed, and gets dropped from the sample.

    Comment by Andrew — April 30, 2012 @ 11:12 am

  3. Nice. The difference between relievers and starters is pretty straightforward I suspect–your most talented pitchers will, by and large, become starters. Even a small degradation in talent level among your relievers can lead to them falling off a cliff.

    Comment by Blue — April 30, 2012 @ 11:22 am

  4. True Blue. Not to mention often times starters get converted to relievers because they have not developed a 3rd pitch, which would further exacerbate their problems with a declining fastball.

    Comment by Redscot — April 30, 2012 @ 11:30 am

  5. Very cool. Thanks guys.

    Comment by MikeM — April 30, 2012 @ 11:31 am

  6. Nice job. I don’t mean to be petty, but these graphs are hard to read. The colors are not very distinguishable, all the lines are the same width and shading (except at the end) and I don’t know why they’ve been printed on a grayish background–that makes it even harder to distinguish the lines from each other.

    Comment by Dave Studeman — April 30, 2012 @ 11:34 am

  7. How curious that swinging strike rates seem to tick up modestly, but K/9 rates implode.

    Comment by Oliver — April 30, 2012 @ 11:37 am

  8. Don’t sinkers and cutters average a bit slower than four-seamers for the same pitcher? Maybe older pitchers are choosing to throw a higher % of cutters/sinkers, making it look as if they have lost more velocity than is actually the case.

    Andrew correctly raises issues of bias in the data. Might some of the observed differences between starters and relievers be due to differences in quality and choices of who starts and who relieves. And might these work differently at different ages.

    Comment by kds — April 30, 2012 @ 11:37 am

  9. I think it’s obvious (especially to us who have lived it) that you are not as athletic as you get older. I would be interested in seeing the data to show that even with decreased velocity a pitcher can still be effective. After all, older pitchers still face a steady stream of young guys even as they age.

    Comment by Hurtlockertwo — April 30, 2012 @ 11:43 am

  10. Totally agree. There’s probably a lot of sample mortality issues (players retiring) in the later years.

    Comment by Spencer — April 30, 2012 @ 11:52 am

  11. Is there any reason you stopped these curves at age 37? Should go out a lot futher.

    Comment by Jamie Moyer — April 30, 2012 @ 12:30 pm

  12. I think one thing that should be addressed in the comparison between a pitcher’s declining velocity and his declining K/9 rate is his increase in understanding of how to approach hitters. A nice comparison piece would be looking at guys who threw two, three, or four pitches throughout their careers. How did their velocity decrease? How did their K/9 rate decrease? My hypothesis would be that pitchers who threw more pitches saw a greater decline in their velocity, but a slower decline in their K/9 rate. It’s easier to set up hitters if you have more pitches, and that fact leads to greater room for improvement.

    Comment by Jake — April 30, 2012 @ 12:47 pm

  13. I would love to see ERA on here instead of FIP.

    FIP is only more predictive than ERA in pitcher’s parks, whereas ERA is more predictive in hitter’s parks.

    EIther use SIERRA, or use both ERA and FIP. There’s no reason to have FIP on there when you already have K/9 and BB/9. Its just a conglomeration of the two.

    Comment by RC — April 30, 2012 @ 12:56 pm

  14. There’s an element of the reverse issue though as well. The young fire-throwers are more likely to enter the league earlier than the tepid-throwers (who may have to master a second pitch or spend time improving control/command in order to get their ticket punched to the show). Even looking at the anecdotal – Oswalt clearly showed no velocity decline until his early-30’s; Zito’s velocity simply looks more erratic (with a clear decline correlated with the size of his contract)

    Comment by jfree — April 30, 2012 @ 12:58 pm

  15. I’m also not a huge fan of adding more data to increase the sample size, when you know that data is less accurate.

    Comment by RC — April 30, 2012 @ 12:59 pm

  16. You can click them and enlarge them and they’re quite easy to read. I think I agree that they’d look a little clearer against a white background but the larger graphs are very readable anyway.

    Comment by chuckb — April 30, 2012 @ 1:00 pm

  17. This is really awesome! Thanks. I look forward to the next rendition.

    Comment by chuckb — April 30, 2012 @ 1:01 pm

  18. The same inherent problem exists in Zimmerman’s hitters series. Tango, et al. used a different methodology than Bradbury for that analysis, which I disagree with. But they at least confronted the inherent issues in their model by explaining the specific methodology they used in the analysis to try and correct for that deficiency.

    So you just have to know going into this that if Zimmerman’s involved that inherent problem is going to be there. My problem with this approach is that for folks like me, and apparently some others, while I like the idea and I think the analysis would be interesting, it’s not even wrong and merely trivia that I won’t much bother with. This sounds like an attack on Zimmerman, but it’s really not. It’s just that when you have fundamental differences, you’ll have separation and disunion.

    Knowing that that was going to be an issue, my bigger beef is that FIP was used here, instead of either ERA (just as reliable over time), or SIERA (even more reliable and most powerful using smaller samples). Since SIERA is probably the most predictive metric we have (hitters or pitchers), it’s a shame that it was not used for an analysis that it is perfectly suited for, and since it has good predictive power for smaller samples, might help correct for some of the fundamental problem noted in the original comment.

    Comment by Paul — April 30, 2012 @ 1:05 pm

  19. 2 for 2.

    Comment by Paul — April 30, 2012 @ 1:08 pm

  20. Go ahead and be Petti. This piece’s author certainly is.

    Comment by Whelk — April 30, 2012 @ 1:28 pm

  21. You’re right. Sinkers and cutters will generally have lower velocities, but there’s currently no public source of trustworthy (or at least consistent) pitch classifications going back multiple years, to separate that out.

    This introduces all sorts of other problems, but I’d like to see these aging curves looking at the top some percent of fastballs in fastball velocity. That might be a quick way of getting mostly four seam fastballs and comparing apples to apples.

    Comment by Whelk — April 30, 2012 @ 1:33 pm

  22. I agree that research would be very interesting.

    Comment by Dan — April 30, 2012 @ 1:49 pm

  23. I did a very rudimentary calculation of sliders and cureball weight values, as compaired to average velocity. There is a positive relationship of weighted value to velocity with breaking pitches, but it doesn’t appear to be as closely related as fastballs are.

    Comment by payroll — April 30, 2012 @ 2:05 pm

  24. I think the sharper decline in skill for relievers, especially in the younger years, might be partly attributed to a bias in the data. With most positions, including starting pitching, young players usually need to impress in the upper minors before they’ll be given a role with significant playing time at the majors. For relief pitchers, it seems to me that teams use the throwing-spaghetti-at-the-wall approach a little more frequently. There are a large number of relievers who are thrown into modern bullpens as question marks, and either they prove themselves and stick or they’re replaced by more spaghetti.

    Consequently, if a reliever has 2 years with a decent number of innings pitched, they probably pitched well enough in the first of those years to earn a secure role for the second year. If they pitched poorly, they probably were dropped, and while they might return to the majors, it may not be for a couple years. This would result in a larger measured decline in year-to-year performance than the underlying change in true talent.

    This selection bias is common to all aging curves, but my hypothesis is that it is more pronounced in relief pitchers due to teams’ approaches in roster construction. I’d like to see this at least addressed in the relief pitcher article, though I’m not sure whether there is a clear solution.

    Comment by Newcomer — April 30, 2012 @ 2:20 pm

  25. Very interesting research. One thing that stands out immediately is that velocity tends to go into rapid decline at a pretty young age. So, if a pitcher is going to have any longevity, he needs to either start out with a very high velocity or quickly learn to pitch without velocity. I’d like to see how different kinds of pitchers age – ground ball pitchers, power pitchers, lefties, etc. One thing in particular I’d like to see is the difference in slopes between power pitchers and finesse pitchers.

    Comment by Lee Panas — April 30, 2012 @ 2:56 pm

  26. If you’ve got a problem with my posts, and are intelligent enough to, please point out specifically what is wrong, instead of posting useless 3 word comments and falsly believing yourself clever.

    Comment by RC — April 30, 2012 @ 3:31 pm

  27. Ive always thought doing curves for pitchers is extremely difficult due to the ability for them to constantly be changing their repertoire/grip/sequencing… looking at FB velo is fine, but when you start looking at K/9, BABIP etc you are opening a whole can of worms. It’s a completely different beast from aging curves for hitters where their skillset doesnt change often.

    Comment by Pat G — April 30, 2012 @ 3:37 pm

  28. It’s not just pitchers’ skillsets that change – it’s their roles as well. Starter, middle relief, LOOGY, closer are different jobs. Aceves has “gained velocity” as a closer, for example. I wonder if it might clarify matters to treat pitchers’ times as starter or closer as their “real” careers, when they have actual value.

    Comment by Mr Punch — April 30, 2012 @ 4:18 pm

  29. This contribution is excellent and much appreciated. Look forward to the rest of your analysis

    Comment by Bill but not Ted — April 30, 2012 @ 5:16 pm

  30. I think Paul was indicating agreement with you there. He had earlier voiced his disagreement with using FIP for this analysis. It appears that also agrees with your objection to adding data which may be unreliable.

    Comment by Mcneildon — April 30, 2012 @ 5:25 pm

  31. Yikes RC, I was just trying to save some time there instead of putting a +1 under each of your comments that I thought were spot on.

    Comment by Paul — April 30, 2012 @ 5:36 pm

  32. Yep, key point. So what did we really end up with here? That pitchers do not throw as hard and are not as “talented” as they age. Maybe I’m in the minority here, but neither of those things surprises me in the least.

    Comment by Paul — April 30, 2012 @ 5:41 pm

  33. Is there information on how much velocity declines for a pitchers based on how much velocity they started with? I feel like (anecdotely) pitchers who start their careers off throwing high 90s see there velocities drop more than pitchers who start off in the low 90s.

    Comment by Dave — April 30, 2012 @ 7:54 pm

  34. Paranoia paranoia everybody’s comin’ to get me

    Comment by JDanger — May 1, 2012 @ 10:09 am

  35. Sorry, my bad.

    I’m just used to getting jumped all over every time I mention that FIP is a pretty terrible stat.

    Comment by RC — May 1, 2012 @ 12:41 pm

  36. “The loss of velocity is important because we see that pitchers’ abilities to record strikeouts follow a curve similar to the speed of their fastballs. However, the slope of the decline is not as dramatic as the velocity decline. This is perhaps do to a couple factors. First, pitchers are likely to further develop secondary and tertiary pitches as they mature…Second, and somewhat related, pitchers might develop a fastball with additional movement — like a sinker or a cutter — to compensate for the velocity decline. This also could lead to a less steep decline in K/9 and SWG_Strike rate than a pitcher’s velocity decline alone might predict.”

    Wouldn’t a more important factor be the scale of the x-axis having inconsistant units? The slope for fastball velocity decline was in mph, but the others are showing decline in K/9, FIP, etc. All of them have different units so we shouldn’t expect them to have the same absolute value decline. Unless I missed something…

    Comment by Noah — May 10, 2012 @ 1:39 pm

  37. Solid!

    Comment by Keith Christoffers — February 15, 2013 @ 9:14 pm

  38. My take on these graphs is that they contain some artefacts from the steroid-era. Certain pitchers lose more than just their age-related velocity, they also lose the little extra once they go clean. Add it up and it should explain the huge drop that some guys experienced over the last 2-3 years.

    Comment by Neric — August 26, 2013 @ 3:22 am

  39. I have a question. Here, why use the harmonic mean vs. some other mean? Why does the harmonic mean make the most sense here? Thanks!

    Comment by tex — June 29, 2014 @ 9:16 pm

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