Pitch Type Performance: 2018 Summary by Alex Chamberlain January 14, 2019 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.) Notes: 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 Pitch GB% LD% OFFB% PU% HR/OFFB BABIP 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 Pitch SwStr% AVG SLG ISO TAv wOBA 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.