Pitch Type Performance: 2018 Summary

Shortly after the onset of last season, I dug into pitch-level statistics to see how much swinging strike rate (SwStr%), ground ball rate (GB%), and isolated power (ISO) varied by pitch type. I felt inspired after analyzing Madison Bumgarner before the 2018 season and noticed his fastball, once elite, was utterly broken after his dirt bike accident. (See his 2018 player caption and this July post in which I followed up MadBum’s lack of progress.) I felt encouraged by the praise the post received from readers and fellow analysts alike for the clarity it provided. I’d like to think it helped move the needle, even if only slightly, in terms of how we evaluate pitchers.

I wanted to refresh the guts of that post for the 2018 season with additional metrics. There’s not much else to discuss; this’ll be short and sweet. (I’ll toss in some gratuitous high-level analysis following these tables.)


  • All data is courtesy of PITCHf/x via Baseball Prospectus
  • All tables present average rates for starting pitchers only
  • Due to pitch tracking/stringing not being perfectly precise, the numbers below are highly accurate but not completely so and may not align exactly with FanGraphs’ batted ball data (for example, Baseball Info Solution strings far fewer line drives than does PITCHf/x)
  • Click headers to sort!

Batted ball outcomes by pitch:

2018 Batted Ball Outcomes by Pitch
Change 50% 23% 21% 6% 19% 0.272
Curve 49% 24% 22% 5% 20% 0.300
Cutter 43% 27% 22% 8% 20% 0.294
Fourseam 34% 27% 29% 10% 19% 0.295
Sinker 52% 24% 19% 5% 20% 0.310
Slider 44% 24% 23% 8% 19% 0.280
Splitter 53% 23% 19% 5% 22% 0.275
SOURCE: PITCHf/x (Baseball Prospectus)

Hitter production allowed by pitch:

2018 Performance Allowed by Pitch
Change 16% 0.237 0.387 0.150 0.241 0.292
Curve 13% 0.221 0.366 0.145 0.223 0.267
Cutter 12% 0.255 0.417 0.162 0.258 0.315
Fourseam 9% 0.263 0.460 0.197 0.282 0.349
Sinker 6% 0.292 0.455 0.163 0.287 0.355
Slider 17% 0.208 0.348 0.140 0.217 0.260
Splitter 18% 0.209 0.342 0.133 0.219 0.262
SOURCE: PITCHf/x (Baseball Prospectus)
TAv = True Average (courtesy of Baseball Prospectus)
Due to limitations with the data, wOBA is approximated (but still highly accurate)

Quick recap:

  • Sliders, change-ups, and curves are good. Four-seamers and sinkers are bad. Splitters are an enigma!
  • Seriously, don’t throw a sinker.
  • No, I’m kidding a little — throw a sinker, but only if it’s actually good. Power sinkers preferred. (Just discussed this regarding Chris Archer recently.)
  • Most pitchers could improve by optimizing their repertoires to include more breaking stuff in place of fastballs, or to more frequently lean on, say, a two-seamer in lieu of a four-seamer.
  • That said, the way a pitcher’s offerings interact is important.
  • Lastly: I’ve seen a lot of analysis using pitch values recently. Pitch values are the ERA of pitch-level analysis, as it’s entirely outcome-driven. Does ERA tell the full story? Never. It can be truthful, yes. However, almost every baseball fan has already learned to approach ERA with a healthy amount of skepticism. Do the same with pitch values. Use the information above to further refine your understanding of pitch values as a description of a pitch’s effectiveness.

We hoped you liked reading Pitch Type Performance: 2018 Summary by Alex Chamberlain!

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Currently investigating the relationship between pitcher effectiveness and beard density. Biased toward a nicely rolled baseball pant. Three-time FSWA award finalist, one-time award-winner. Featured in Lindy's Sports' Fantasy Baseball magazine (2018, 2019).

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7 Comment authors
eotisAlex ChamberlainSucramRenrutcavebirdChippersJonesing Recent comment authors
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Good stuff Alex.

What do you mean by “power” sinker? Is there a certain minimum velo threshold?