Let us take some time to appreciate the Waxahachie Swap. The term was coined by Rob Neyer and describes a maneuver occasionally pulled by a manager, usually in the National League. Suppose you have a pitcher on the mound—a right-handed gent—and the other team has a left-handed hitter on the way up. You’d really rather have that lefty face your LOOGY, but bringing in your LOOGY means that the current pitcher had to go take a shower and can’t come back until tomorrow. And that makes you sad.
But you don’t have to be sad if you have the Waxahachie Swap. Your right-handed pitcher can simply go play left field for a batter and the LOOGY can come in to take on that tough left-handed bat coming up. OK, so it’s a little bit dicey having a guy in left field who isn’t actually trained to play there, but what are the chances that will come back to bite you? You do lose your left fielder for the rest of the day (and will need to eventually plug in your fourth outfielder out there when all the swapping is done), but it’s worth it, right?
This seems like the sort of thing we should see more of. Right?
Warning! Gory Mathematical Details Ahead!
There are a lot of moving parts on this one. Like any strategy, it has to be evaluated both in terms of what might conceivably happen because of it and what might not happen because of it. It’s a maneuver that can work out great, but also one that can go horribly wrong.
Let’s start with a bit of context on how to evaluate. This move is more likely to take place during a situation of higher leverage. No one would bother to do this, or even to play matchups, when the score is 9-1. From 2012-2016, 79 percent of relief appearances that lasted only one or two batters began with the score within three runs (in either direction). We need to keep that in mind.
But let’s start with the obvious benefits of the Waxahachie Swap. If done right, it allows a manager to take the platoon advantage against an extra batter, without having to sacrifice another relief pitcher to get it. In 2016, for a left-handed batter, that was worth 87 points of OPS and for a righty, 38 points. That’s a lot. But in one plate appearance, that’s worth about .025 runs.
It comes at a cost. Presumably, the pitcher on the mound will go out to left or right field. It’s likely that the ball won’t even be hit near to him. From 2012-2016, only 8.7 percent of plate appearances ended with either a fly ball or a line drive that the left fielder eventually fielded (whether to catch it or pick it up when it stopped rolling). We also know that most fly balls fall into either the category of “any competent human with a glove on his hand could make that catch” or “no one was going to get to that.” The spread between good fielders and bad is generally on a small subsample of fly balls per year.
It’s hard to know how good of a left fielder the average pitcher would be. Pitchers do shag flies during batting practice and some probably played the position in high school or college. I’ve estimated that the difference between an average left fielder and a really bad one is about .02 runs per inning, and we’re not talking about a full inning here. So, we’ll dock our pitcher moonlighting as a left fielder about .005 runs for his time out in left, on a per-plate appearance basis. That still leaves roughly .02 runs of profit.
So why isn’t the Waxahachie Swap more common?
One reason might be that managers think it’s disruptive to have a pitcher face a batter and then effectively sit out for a while, and then re-enter the pitching frame of mind. The swap happens so infrequently that we can’t truly test that proposition, but we do have something analogous. I looked for pitchers who entered a game with two outs in an inning, finished off that inning, and then returned for the first batter of the next inning. I compared these “spaced” plate appearances to the second batter that relievers faced in a consecutive sequence, and found that, controlling for batter and pitcher ability, we didn’t see any differences in the two groups.
The real difference-maker is something that you might not expect. At the end of the Waxahachie Swap, the original pitcher comes in from left field to resume the pitching mantel, but the original left fielder is now out of the game, and someone has to take his place. Most of the time, that means swapping out a team’s starting left fielder for a replacement-level bench player. Because left fielders are generally chosen for their prowess with the bat, it probably means an offensive downgrade. The distance between a backup-level left fielder and a starter over one plate appearance is about .02 runs. Poof! There goes all the profit.
Now, it’s possible that the left fielder’s spot in the lineup just passed, meaning that, if it’s late in the game, he probably won’t be coming up again, and the sub’s worse bat won’t make a difference. But let’s consider again when teams generally make these moves. Looking back to those relief appearances that lasted only one or two batters, we see that most of them happen in the sixth, seventh, and eighth innings. Of course, the earlier in the game it is, the greater the chances that the left fielder's spot in the lineup will come up again. And the later in the game it is, the more likely a team is to have a reliever in the game who can be trusted against lefties and righties. Even if a manager is playing matchups, the fact that it’s later in the game means that they don’t have to worry about saving bodies for the rest of the game.
So, the strategy itself probably doesn’t have all that much going for it in expected value, and we have to account for the fact that teams don’t make decisions in the dry vacuum of expected value all the time. There’s the reality that while it’s not likely that the pitcher moonlighting as a left fielder will be exposed… well, there’s always that time. And turning a fly-ball out into a fly-ball single is a big deal in terms of linear weights and, considering that we’ve already established that the game is probably relatively late and close, it’s a big deal in the … ummm, how to say this … actual game.
And to be honest, in a bullpen filled with seven or eight guys, you can get the same sort of platoon effect by just using three pitchers and not taking the risk with the pitcher in left field or losing the left fielder’s bat. So, it would probably take exactly the right set of circumstances for it to make sense, although the thing that might make it work the best is having a starting left fielder whom you don’t actually mind removing from a game. It’s tough. Even then, there’s a cost that we haven’t considered. Burning a position player like that means that later on in the game, a manager has one fewer option when it comes to pinch-hitting in another situation. That has a cost too, although that one’s harder to pin down. But it’s there. And suddenly, we’re potentially in negative territory.
It’s possible that if the two pitchers alternated over a couple of hitters, and maybe made a couple of trips back and forth, thus grabbing multiple extra plate appearances with the platoon advantage, it could turn a profit. However, that opens a team up to more risk for that ball that finds the pitcher in left field. I can see why it doesn’t happen very often. Just because something feels like living dangerously and isn’t done often, it doesn’t make it a “good, but underappreciated strategy.” There might be cases where everything lines up and it would sorta make sense to do the swap, and so we’ll see it once in a while. But sadly, as cool as it is, it’s going to have to be a once-in-a-while thing.