It seems almost trivial to rehash reliever volatility, because it’s been so clichéd for over a decade now. Perhaps it’s still worth saying. Baseball players, in general, are the most volatile of any sport I know, and relievers the most in baseball. Andrés Muñoz has been burdened with one of those years they have. Earlier in the season, he described an outing as the worst he’s ever had, which makes sense. He’s struggled with the command of his slider, and he’s struggled with his fastball command. Sometimes at the same time. He clearly hasn’t been himself.

The worst of Muñoz’s struggles with his four-seam fastball date back to 2025, but it wasn’t until earlier this year that he started cutting the hell out of his fastball, meaning he’s throwing it much more inefficiently, or with less active spin. That’s not always bad, but with a four-seamer, it usually is. Here’s what the drop in spin efficiency did to his fastball: