i think folks sometimes treat xERA for pitchers as being as good as xwOBA is for hitters, but that's not really the case. primarily because batters have significantly more impact on exit velo than pitchers

Updated Roki plots now that I fixed the slider issue on his FK. Better grade on it and the four-seam, plus the added sinker, and a SL that looks significantly better than the old SW. Was skeptical of him coming into the year, but this seems relatively thorough

how did I not catch that, that's a bug in how I'm doing the slider because there's not a broad population of forkballs to compare it to average. Here's his metrics in table form '26 vs '25

Roki's arsenal is grading out better this spring vs last season. StuffPro likes the SL over last season's SW and likes some velo coming back to the four-seam

new cubicle decor, spiderman is protecting me

I taught my coding agent to think like a Bayesian, and wrote up what I learned. LLMs know #BayesianStats but skip half the workflow. So I built an open-source Agent Skill that enforces the full workflow every time Works with Claude Code, Cursor, Gemini, etc. learnbayesstats.com/blog-posts/b...

@swingsandtakes.com whoa I missed this, congrats!!

every generation of human has enjoyed throwing rocks and sticks into bodies of water

Some interesting names in the StuffPro standouts from spring so far. Collyer surprised me, and Lagrange I clearly haven't been paying enough attention to.

lest I allow myself too much optimism, Strider's looking like he's headed for a repeat of '25 stuff-wise

JR Ritchie's arsenal is also looking good

Didier Fuentes's new slider looks impressive, and he's had good life on the four-seam this spring. Try not to make too much of spring data, but this is really encouraging

how to do your taxes: 1) do your taxes 2) periodically log in anxiously and review everything, repeat 2-3x per week for 7 weeks 3) click file 4) get scared, back out, repeat step 2 5) file taxes

Wrote about Russell, a very significant figure in my brain pebblehunting.substack.com/p/what-russe...

it's a beautiful tunnel www.baseballprospectus.com/news/article...

this is great

Asked Augie what’s special about her she said green donut asked Georgia and she said she gives rainbows to kids who don’t have rainbows on their shoes

in case you've never seen it, this is Roger Ebert on The Mummy

studying ball flight only tells you so much about how batters detect which pitch type is coming. in games they use a ton of biomechanical info from the pitcher's delivery as well to give them a strong prior ahead of ball release. cool paper studying that: arxiv.org/abs/2603.048...

*fifty pages into a book about bruce springsteen* “and this guy is bruce too?” *flip* “whatabout this guy, are he bruce?” *flip* “oh i tink he’s bruce”

got to read to the girls' daycare class today, they were so excited to show all their friends the book and tell them what happens next

i cannot express how much i hate this

hilarious to me that the twins of two engineers' first time on tv was them doing engineering

sturgill has a classic country album, a psychedelic country album, a jazz/blues/country hybrid album?, a rock album, two bluegrass albums, a country concept album, a jam band album, and now this. what a career

Congratulations to all winners of the 2026 SABR Analytics Conference Research Awards! @michaelrosen.bsky.social of @fangraphs.com @richstaff.bsky.social of @defector.com @rjandersonwrites.com of CBS Sports @depstein1983.bsky.social of @baseballprospectus.com sabr.org/latest/rosen...

Cool video from @lancebroz.bsky.social on using AI tools to create baseball apps youtu.be/rTBJjHosIgg?...

very important app development activities happening

one thing i've come to appreciate since becoming a parent is 100 piece puzzles are a lot of fun for all ages

living her best life

movement plots inspired by classic car gauges

cool use of their new tools blogs.fangraphs.com/logan-webbs-...

Personally never understood this concern. Who cares if it is a mess? The tariffs were straight-up theft. Do we look the other way on robberies because the criminal was too successful? I hope it *is* tremendously painful and makes the government never want to try this again.

a glimpse at a powerpoint slide i’m making

this is so cool, well done by the FG team blogs.fangraphs.com/introducing-...

webbing up the bad guys!

claude's just like me

I still think the internet is the best comp for AI. It was a bubble that popped, but the underlying tech turned out to be real. It enabled a bunch of psychosis and slop, but also some genuinely cool stuff. Massive labor market disruptions, but employment levels look about the same.

meet Mug Guy

can't believe they cracked this code-

i've been going through and updating my passwords on all of my accounts, and good lord i forget just how many websites i have logins for. this is like a week long task

We coded our ~100k articles using LLMs. Should you believe them? To answer this, we benchmarked 4 human RAs against 3 LLMs on their ability to recover ground truth article data. Details in the paper and appendices, but the LLMs did well and handily beat the highly trained humans.

well this is absolutely fascinating: "Neural Sabermetrics with World Model: Play-by-play Predictive Modeling with Large Language Model" arxiv.org/abs/2602.070...

We have a landing page with the downloadable spreadsheet and all the PECOTA 2026 articles right here, for our subscribers. I know some people had issues downloading the spreadsheet this morning, that should be resolved.

to start us off on PECOTA Week, @bachlaw.bsky.social wrote about if/how the model has been updated and what would actually be a major impact in the future, if it becomes available:

just a heads up that PECOTA Week starts *TOMORROW* at @baseballprospectus.com. We do our best to respect everyone's Super Bowl hangover today (though we have many good articles up), but our projected standings, and PECOTA-based tools, plus a slew of articles will open up TOMORROW. I'm excited.

This was a fun conversation! Got to talk about the batter's eye in Seattle and the Brendan Donovan trade, and got to hear from Stephen on his past (and future!) work on swing processes.

my new website is done www.andrewhirsh.media

Got to be on Vince Gennaro's show last night talking about my piece nominated for a SABR award, was a lot of fun and he was a great host! Be sure to check out @swingsandtakes.com at the beginning of the episode too! www.siriusxm.com/player/episo...