With Gausman it's usually as simple as locating his fastball down in the zone well enough, especially early. You can pretty much scroll through his game logs, find the ones where his swing and miss sucks, and see his fastball locations were mostly up, which allows hitters to just "see low, let it go" because they can reasonably guess it's a splitter that won't be a strike. In games where his fastball location is down more than up, he's laughing