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I see Gavin Williams' Fangraphs Stuff+ on the Slider at 107 for this outing so that probably makes more sense with the changes you described. Also, are change-ups tough pitches to evaluate in terms of Stuff+? I see Cole Ragans got 9 whiffs on his, but his Stuff+ only at 77. Does this mean that Stuff+ is not too good at grading offspeed pitches or that Red Sox hitters are bad at hitting change-ups or that he was sequencing and locating very well? (Maybe a mixture of all of those things lol). Love the notes and thanks again!

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Changeups are notoriously funky in models. Mainly because it has to do more with how CHs interact with the pitcher's fastball (how much more does it drop? how much slower is it?)

To me, it's the one pitch where you should just look at results (swing-miss, contact quality, location, etc) and determine quality that way. If I was only given one thing to look at for a CH, it would be something like location or swing-miss, not stuff+. Doesn't mean it's not valuable, just less valuable than it is for other pitches to me.

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Got it, thanks! Does change-up grade have a lesser weight in a pitcher's overall Stuff+ grade? Also, then someone like Grayson Rodriguez who has a high Stuff+ changeup just means that he has good separation in movement and velocity between his offspeed and fastball?

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My belief is that overall Stuff+ grade is more of a usage thing. It's essentially multiplying stuff+ of individual pitch types by their usage. So would depend on how an individual pitcher mixes their CH in. Also could be a reason to look splits as important. 112 Stuff+ could be because the guy has a banger SL that helps his Stuff+ score but gets pounded by lefties.

Grayson is a good one, yeah. He's getting above average velo separation and above average drop separation, so stuff+ models are going to like it a lot. You generally want some balance of the two. Hard CHs with a lot of drop separation are generally the best. So not just max velo and drop sep that works best.

And again, I still prefer location for a lot of changeups and other performance metrics.

I did a video on this a bit ago, might distill some of this: https://youtu.be/QIa52IEOqkE

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Awesome, thanks! Will definitely check it out

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