The Platoon Advantage Will Mislead Youon August 17, 2020 at 5:15 pm

The Platoon Advantage Will Mislead You

It’s easy to make light of the job of a baseball manager. Fill out a lineup card, pull your pitchers when they’re tired, and don’t call for any bunts? It often feels like we could all do that. Whenever I start feeling like it’s a cinch to manage, I think back to something my dad told me when I was younger: the manager’s job is to put his team in the best position to win.

Granted, that was before the sabermetric revolution, so managers weren’t necessarily doing a great job of it, but putting their team in the best position to win has always been the point of the job. If that sounds easy, so be it, but there are plenty of ways to mess it up, which means every decision a manager makes has the potential to be the thing they did that led to a loss.

With that theory of managing in mind, I did a double-take when I saw the Astros’ lineup on Sunday. Facing lefty Justus Sheffield, Dusty Baker submitted this lineup:

In a lot of ways, that’s a satisfying lineup against a left-handed pitcher: seven righties against just two lefties after accounting for switch-hitting Abraham Toro, and some big boppers among those righties. Seeing Josh Reddick batting second set alarms off in my mind, though.

Reddick is a perfectly nice platoon player, with a career 111 wRC+ against right-handed pitching in more than 3,000 plate appearances. Against lefties? He sits at a 91 wRC+ in 1,200 PA. A good rule of thumb is that you should assume lefty batters are 8% better with the platoon advantage than without it. Reddick’s long career and 10% platoon split suggest that he might be even more vulnerable to southpaw pitching than the average lefty. Given that, what business did a 91 wRC+ hitter have between George Springer and Alex Bregman?

My dad’s advice rung clearly in my head: Baker wasn’t putting the Astros in the best position to win. Reddick is a below-average hitter against lefty pitching, and there he was, holding down arguably the most important lineup spot in a powerhouse batting order. If he did it on Sunday, how many other lineups had weird platoon holes like that? I endeavored to find out.

To test this theory, I looked at every plate appearance made against a starting pitcher this year. When bullpens get involved, platooning is a very different game, and I wanted to focus specifically on the part of the job that occurs before any pitches are thrown: lineup management. Good news: the Astros are 25th in baseball this year when it comes to seizing the platoon advantage. They’ve had it in 51% of their plate appearances this year, miles below the league average of 59.5%. We did it! Article over!

Bad news on that front — the Astros actually had the platoon advantage less often last year, in only 46% of their plate appearances, the second-worst rate in baseball. Has Baker been making improvements, glaring Reddick-batting-second holes excluded?

Like so many articles I write, I regret to inform you that this one is a trick, based on a false premise. I think that the best way to show it is to take a look at the full leaderboard:

Cleveland is in first place by a ton. Why? Here’s RosterResource’s projection of their everyday starting lineup against right-handed pitching:

Five switch hitters, including the first four batters. It’s impossible not to have the platoon advantage most of the time. This lineup has more righties than lefties in it, and yet it already has a handedness edge two thirds of the time against a righty. When they face a lefty, it’s downright unfair: they can substitute Jordan Luplow for Naquin and present a lineup of five switch hitters and four righties, a perfect 100% platoon advantage.

Is that good managing? Not really. It’s simply playing your best hitters as much as possible — in this case, they happen to mostly be switch hitters, which means the Indians are at the top of this list not because they’re consciously hunting out a handedness edge, but because they’re consciously playing their best players as much as possible.

Similarly, the Yankees have the platoon advantage only 38.6% of the time against starting pitchers, the worst mark in baseball by a mile. Why? Here’s their Opening Day lineup against Max Scherzer:

Look at all those righties against a right-handed pitcher. And yet, who are you benching here? Aaron Judge, Gleyber Torres, Giancarlo Stanton, and Gary Sanchez are all good enough hitters that they’re better than whatever lefty option the Yankees could replace them with, platoon edge or no. DJ LeMahieu has been injured this year, but he’s also a righty lock when healthy.

The Astros are in a similar boat. Why do they have the platoon advantage so rarely? It’s because they play Springer, Bregman, Correa, and Altuve against everyone. Most pitchers are righties, which means they rarely have a handedness edge, but they succeed anyway, because they’re great hitters. In other words, which teams have the platoon advantage most and least often is often just a proxy for which handedness their best hitters are, and whether they have hitters good enough that they should play every day regardless of matchup.

Want to figure out which managers are putting their team in the best position to win? Looking at lineups is a great way to do it. Great managers get their best hitters in as much as possible and fill in the cracks with role players in positions where it’s easy to succeed. One thing you shouldn’t do, though, is try to make sweeping generalizations based on data as inexact as how often a hitter gets to face opposite-handed pitching.

Did I do that, just now? I sure did. But I hope you’ll forgive me, because I did it to prove a point. Dusty Baker really did make an odd decision, and one I strongly disagree with, by batting Reddick second in a spot where he was set up to fail. He failed, by the way — in three plate appearances against Sheffield, he made three outs.

The error isn’t that we shouldn’t care about that decision. We should! It’s bad! The error, rather, is when I count Reddick-vs.-lefty the same way I do Bregman-vs.-righty. If you zoom out too much and abstract away individual players, you’re risking this type of error. Every player isn’t created equal, and every lefty-on-lefty matchup isn’t the same; you wouldn’t expect the Dodgers, for example, to sit Cody Bellinger against southpaws. Managing is about putting your team in the best position to succeed — emphasis on your team.

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