Will the Cubs Platoon Michael Busch? Should They?

We live in the age of optimization. It's not always ruthless, and it needn't be, but by and large, teams shield even some of their best players from matchups they view as difficult for them. That especially means that left-handed hitters see lefty pitchers less often. It's easy to miss that trend, because of the way rosters and rules have changed over time, but it's true. First, consider this chart, showing the percentage of all plate appearances that have featured left-on-left matchups over the last 110 years.

I've added the trend line, not to suggest that it matters how closely any given season hews to that line, but to make clearer the general direction of change. Lefty hitters are seeing lefty pitchers slightly more often than they historically have, though markedly less than they did about a decade ago. That would seem to go against the claim above, right?

Wrong. We have to correct for a few things. To wit: there are more left-handed pitchers than there used to be, too. 

Don't obsess over the apparent slopes of these trend lines, or anything. The charts are on different scales. As you can see, though, southpaws have become more prevalent over time (though they have made up a smaller share of all pitchers since the last rounds of expansion, in the 1990s, than they had before that). So, too, have lefty batters.

Take those confounding factors out, by boiling things down to the share of all lefty plate appearances taken against lefties, and you can see what's really happening. 

There's no good way to show it to you graphically, but take the above and mentally factor in one more thing: Benches are tiny now. In the middle chunk of the 20th century, when Casey Stengel and then Earl Weaver ruled the game through assiduous use of platoons, they had 16 or 17 position players on their rosters, and could smoothly run two or three platoons at any given time. Only their very best regulars faced same-handed pitching on a regular basis. 

The 13-man pitching staff makes that virtually impossible. You have fewer players on your bench, and they have to be used differently. By the time you ensure that you have a backup catcher, a shortstop-capable infielder, and a center field-capable outfielder, you're left with just one bench spot to award to a player selected purely for their bat. Many managers don't feel empowered to use those guys as aggressively as they used to, either.

So, let's get to Michael Busch. One reason why the Dodgers were willing to move on from him is that, because Busch has relatively little defensive value, he needs to hit exceptionally well in order to be more than an average contributor. Lefty hitters struggle with lefty pitchers, partially because they're given few chances to acclimate themselves to facing them, but also partially because those pitchers are getting nastier all the time. As a group, lefty batters haven't had an OPS north of .700 against southpaws since 2019 (thanks largely to the aeroball), and before that, it's been since 2009. If Busch is limited to platoon work, it really limits his ceiling.

I don't think he needs to be thus limited, though. Last year, across Triple A and MLB, 112 batters had at least 100 plate appearances in left-on-left situations. Among them, Busch ranked:

• 13th in average exit velocity
• 40th in hard-hit rate
• 12th in launch angle sweet spot rate
• 9th in contact rate on swings
• 30th in chase rate on pitches outside the zone

This is cheating, a bit. Since most of Busch's sample was against Triple-A pitching, we're not comparing apples to apples--or if we are, some of them are honeycrisp and others are red delicious. It's not perfectly equitable.

Still, these data tell the story of a guy who deserves to be one of the few lefty batters entrusted with regular work even against lefty pitchers. If Busch comes to camp and shows the same ability to hang in against lefties that he showed last season, it ought to shape the Cubs' plans for him. That could mean making Christopher Morel more available in trades. At face value, Busch and Morel seem like potential platoon partners, but Morel has reverse platoon splits for his career, anyway. Unless the Cubs decide that one or the other has more defensive value than is generally perceived right now, they overlap pretty significantly in their potential areas of contribution, and that might push Morel out the door if the right offer comes in.

Barring that, Busch's competence against same-handed hurlers still means good things. If he's an everyday first baseman, rather than one who needs to sit once or twice a week to dodge a lefty starter, he brings more value as an individual and gives Craig Counsell more options elsewhere. He's still unlikely to be the next Anthony Rizzo, but when you break down Busch's numbers and see this surprising balance in his game, you can start to understand how he still gets to All-Star status without being able to play a valuable defensive position or bringing outstanding athleticism to the table.

Are you comfortable with Busch facing lefties, at least right now? Does it tinge your opinion on the Cubs' presumed pursuits of guys like Rhys Hoskins?

Research assistance provided by TruMedia, and by Stathead, by Baseball Reference.