When Ken Giles Struck Out Everyone and Then Some
Something happened the other day that hadn’t happened in nearly 17 years, and had only happened twice in the last 50. Not counting Little League, I mean. It happens all the time in Little League. It happens in Little League because catchers aren’t great at catching the baseball, relatively speaking. Little League catchers aren’t great at catching the baseball, and there’s a (bizarre?) rule where batters can attempt to advance on dropped third strikes, and so we’ve all seen plenty of batters reach on strikeouts while we sigh from our positions on the field and wonder how we’re going to sneak out of our friend Gabe’s house to hang out with the girls across the street once Gabe’s parents go to sleep later that night. And then we hope our team’s pitcher strikes out the rest of the guys, too, because striking out more batters than there are outs in an inning is fun.
But it doesn’t happen as often in the big leagues, because, y’know, catchers are good. When it does happen, it’s usually because the pitcher’s stuff is so nasty that it becomes difficult to catch, even for the catcher. When it does happen, it’s also usually four batters in one inning. It’s rare, but it happens. Using the Baseball-Reference Play Index, I ran a search spanning the expansion era, looking for relief outings of exactly one inning with at least four strikeouts.
The results of that search:

Dating back to at least 1985, there are 19 instances of a pitcher whose entire outing consisted of one inning, and four strikeouts. There are plenty more instances of four-strikeout innings, of course, mixed in with the rest of a relief outing, but these are the only guys with one, clean, four-strikeout inning. Nineteen different guys, although two of them are named Mike Stanton.