Longoria's One Strike Plate Discipline

Last week I began work on the question, artfully illustrated by Jason Hanselman, of why Evan Longoria apparently loses his conception of the bottom of the strike zone when he gets into a one strike count. If you haven't read those previous pieces, go do so now. Jason's is here, and mine is here. For those who don't feel like backtracking, here's the heart of the setup:

I don't think there's any reason to purposefully expand your zone as a batter once you get to one strike. That's something you do with two strikes, and in fact, Longo does—he swings more outside the zone with two strikes than he does with one, and he actually makes more contact on low pitches. What we're seeing here is Longoria being fooled. What all of those swings beneath the zone show is the clear and wonderfully isolated effect of successful pitch sequencing.

In one strike counts overall, Evan Longoria swings at 38% of all pitches thrown below the strike zone. That means that to be able to confidently say that I've found the reason his plate discipline deteriorates with one strike, I need to find a situation in which he swings at more than 38% of the pitches below the zone. (I know that correlation doesn't imply causation, but bare with me. Implying causation is tough.)

Well, Longoria swung at 18 of 38 low pitches with negative vertical movement (low and moving lower), for a 47% swing rate. That's interesting (and makes logical sense), but it doesn't explain why he was able to lay off these very same pitches in one strike counts. What if instead we look at the difference in the vertical movement of the one strike pitch from the previous pitch (for instance, if a pitcher throws a fastball that rises 10 inches, and then a curveball that sinks 10 inches, the difference is 20 inches)?

Considering every low ball that dropped more than the previous ball yields a swing percentage of 43%—higher than Longoria's overall swing percentage in one strike counts, but lower than if we just look at the vertical movement of a pitch individually. What's more, there's all sorts of fun that could be had with arbitrary endpoints. If I instead pulled only the low balls that dropped more than the previous pitch by less than one inch, I would have Longo swinging on nine of eleven, for a whopping 82%. There's almost surely something to be found here, but I really don't know how I should define the bins, so I'm going to give vertical movement a rest for now.

Previously, I looked at what Longoria has done on a low pitch after being called for a strike looking. The results didn't make very much intuitive sense, but they got me thinking about whether the pitcher or the batter has more to do with this "sequencing effect." I decided to take a look at pitches in the strike zone that Longoria had either swung and missed on or fouled off. If Longo hadn't swung, these pitches would almost surely have been called strikes looking. (For those interested, including swinging strikes and foul balls outside of the strike zone wouldn't have added many data points. Longoria's one strike plate discipline is quite good.)

While Longoria's swing percentage on low pitches after he's just swung and missed is in line with or slightly below what we would expect in a one strike count, he does seem to be swinging more after fouling a pitch off. Perhaps after a foul ball, Longoria thinks he's almost got the pitcher timed up and gets overeager. Alternatively, I've heard Longoria say that when he feels like an at bat is getting away from him, he steps out of the box and concentrates on the top of the left field foul pole to resettle himself. Maybe he does that after swinging and looking strikes but not after foul balls. Maybe he should do it after them as well.

All in all, there's too little data from one season's worth of at bats, and I know too little about the effects of sequencing on batters generally, for me to say anything for sure. I still think the discrepancy between Longoria's plate discipline on low pitches with no strikes and with one strike is fascinating, and I hope to come back to this some day once I've learned a bit more about how the league as a whole fairs in these same situations.