No Reason to Worry About Halladay

Ken Rosenthal of FOX Sports has noticed some changes in Roy Halladay:

Halladay is using his trademark two-seam fastball 10 percent of the time, compared with 27 percent in ‘11 and 30 percent in ’10. His average fastball velocity is 90.1 mph, compared with 91.4 mph in ‘11 and 92.8 mph in ‘10.

He is throwing 51 percent cutters, 23 percent curveballs and 16 percent splitters, all increases over the past two seasons (Halladay had thrown only 13 percent curves through four starts in ’11 and 14 percent in ’10.).

Halladay’s velocities on all of those pitches also dropped from ’10 to ’11, and they’re down again in ’12. His cutter has gone from 92.1 mph to 90.5 mph to 88.7 during that time.

Not to pick on Ken, because he does fantastic work and is invaluable to the baseball community, but he ticks off a couple of boxes in Mike Fast’s “what not to do with Pitch F/X” article from a couple years ago at The Hardball Times.

Rosenthal mentions Halladay is using his two-seam fastball less. Fast wrote:

The pitch classifications in the PITCHf/x data, as shown on Brooks Baseball, Texas Leaguers and Fangraphs (not to be confused with the BIS pitch classifications also on Fangraphs), are done by an algorithm developed by Ross Paul at MLB Advanced Media. Ross has made significant updates to this algorithm every year, and one of the most noticeable impacts is that the percentage of pitches classified as two-seam fastballs has increased with each update. This does not mean that the pitchers themselves have changed anything about their pitch selection or the movement on their pitches.

If you want to know if a pitcher has really added a new pitch type, explore his data on a site like Texas Leaguers and see if he’s added a completely new pitch cluster from the previous year. Don’t pay attention to how the pitches are labeled; learn for yourself how the different pitch types behave. When you have mastered that, then you’re ready to identify when a pitcher has added a new pitch.

[Update: I originally said that Rosenthal wrote that Halladay was using his two-seam fastball more often, which was incorrect. I have made the appropriate edits, and apologize for the error.]

Rosenthal also notes a decline in velocity for Halladay. This article by Tristan H. Cockcroft at ESPN notes that fastball velocity is at its lowest in April and gradually increases with each month as temperatures rise.

Those March/April numbers are noticeably low, easily the worst in any single month, and while you might claim that less than a half-mile per hour difference between those April and May numbers is small, remember those numbers were accrued over several hundred thousand fastballs per year, and more than 50,000 per month. That’s one monstrous, whopping sample, and it shows that in “blanket statement” form, there might indeed be something to the dead-arm theory.

Rosenthal gets into Halladay’s pitch selection breakdown. While the shift in percentages may seem significant (13 to 23 percent on the curve, for instance), it’s only four starts. Per ESPN Stats & Info, Halladay’s pitch breakdown is as follows:

  • Fastball: 57
  • Cutter: 206
  • Change-up: 68
  • Curve: 98
  • TOTAL: 429

What if Halladay had an off-night where he wasn’t feeling one of his pitches, so he decided to lean on his curve? That could have been the case on April 16 against the San Francisco Giants, when 31 of Halladay’s 109 pitches (28 percent) were curves as opposed to his previous start, when he went to the curve for 23 of his 109 pitches (21 percent) against the Florida Marlins on April 11.

What if Halladay was facing a lineup that was comprised mostly of hitters who are weak against the curve? The Giants’ lineup featured three consecutive left-handed hitters in the 5-6-7 slots: Aubrey Huff, Brandon Belt, and Brandon Crawford. 14 of Halladay’s 31 curves (45 percent) were thrown to those three hitters exclusively. He threw only three curves against right-handed hitters throughout his entire start.

With a sample of only four starts, the effect one outlier can have is enormous. Sure, it’s possible that Halladay is wearing down after throwing so many innings season-in and season-out. But we must be cognizant of small samples this early in the season and be aware of our human tendency to look for stories where there may not be one.

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52 comments

  1. LTG

    April 24, 2012 09:40 PM

    “It’s ALL of that substantive stuff, PLUS the fact that we went 7-9 in the first 16 games (we fell behind 5 games, played below our expected pace, and with only 9/10 of the games remaining to catch up).” I agree that this argument will get you your conclusion. But it is not the same as the one based solely on the win-loss record, which is the one to which Michael originally responded.

    “Of course anything can still happen, but I’m a stats guy, and the 7-9 start lowered the chance of us winning the division, something I cannot ignore. ” I also agree that the start lowers the chances of the expected outcome, but I disagree that this requires epistemic revision because the lowered chances do not pass the threshold.

  2. Phillie697

    April 25, 2012 12:34 PM

    I can handle disagreements :) I don’t like being outright dismissed :)

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