Are You a Starting Pitcher Who Wants the Platoon Advantage? Too Bad!

I was contemplating Astros right-hander Hunter Brown the other day — I imagine this is a topic many of you contemplate regularly as well — and when I looked at his Baseball Savant page, I found myself a little nonplussed:

Brown is one of those pitchers who throws three fastballs; his exciting midseason turnaround owes much to the addition of a sinker. But wow, he’s thrown a lot of fastballs to left-handed hitters, hasn’t he?

It’s not as skewed as it looks; when it comes to fastballs, Brown has a special pitch for hitters on the right side of the plate. (If you hear a thumping sound, ignore it. It’s the late CIA director Allen Dulles, pounding on the lid of his coffin because he heard “special pitch for the right” and has been brought back from the dead by sheer force of FOMO.) Brown has thrown about as many fastballs total to each kind of hitter.

But even that’s a little odd. When it comes to the platoon splits for major leaguers, the rule of thumb I use is two-thirds right-handed, one-third left-handed. You may have noticed me using that number heuristically in my analysis here. It’s not, however, a precise representation of the major league population.

To be clear, Brown is a bit of an outlier. Through Monday’s games, there were 321 pitchers who had thrown 750 or more pitches in the majors this year. Brown had thrown the ninth-highest percentage of those pitches (56.8%) to left-handed batters. In fact, his teammate, Spencer Arrighetti, was no. 2, so maybe there’s something about the Astros that attracts left-handed hitters.

So far this season, starting pitchers have been responsible for more than 88,000 major league plate appearances. Based on pitcher throwing hand and batter hitting side, here’s how those plate appearances have been distributed:

So yeah, turns out the median right-handed starter actually faces slightly more left-handed hitters than right-handed. And it’s not a 2-to-1 split; it’s almost 3-to-1 for pitchers. For hitters, it’s more even — 57.6% to 42.4% — because of switch-hitters, and kids who grew up with overly ambitious parents who turned them into bats-left-throws-right guys because that’s the most advantageous combination for a major league player. (This being the sad interregnum between the major league careers of Pat Venditte and Jurrangelo Cijntje, there are no switch-pitchers in the big leagues at the moment.)

But between switch-hitters, platoons, stacking the lineup with righties against tough lefties, and so on, the net outcome is that most of the time, nobody has the platoon advantage.

Well, nobody except left-handed hitters:

There are so many right-handed people in baseball that right-handed hitters are operating against same-handed pitchers… OK, this is almost exactly 2-to-1, it turns out. But there are enough switch-hitters and left-handed hitters in the game that opposing managers can just barely get over the hump against right-handed starters.

I’d show you a table of the pitchers who operate without the platoon advantage most frequently, but it’s basically congruent with a list of left-handed pitchers. The first 62 pitchers on the list are left-handed, followed by Gerrit Cole, then 11 more lefties, then Arrighetti.

But the pitcher who faces the fewest lefties of anyone in baseball is Tarik Skubal. Garrett Crochet is fourth-lowest, followed by Chris Sale. Framber Valdez, Blake Snell, Ranger Suárez, and Cole Ragans are in the top 15. These are some of the best left-handed starters in baseball. But also in the top 15? Kyle Freeland, Patrick Sandoval, and Jordan Montgomery.

So when managers take all the lefties out of the lineup against a left-handed starter, is it because the starter kills left-handed hitters and every out is precious? Or is it because anyone can hit this joker, so this is a soft target for the right-handed part-time players who need a soft target?

It’s a little of both.

In general, the pitchers who face the most left-handed hitters are lefty relievers, who operate with the platoon advantage twice as often as starters. The LOOGY may be an artifact of days gone by, but the LTOGY (“litoogie” or “Lieutenant Ogy”) seems to be going strong in spite of the three-batter minimum. Let’s zero back in on starters.

League-wide this season, left-handed pitchers have faced left-handed batters 27.9% of the time and surrendered a wOBA of .294 against them. Right-handed pitchers have faced lefties 48.2% of the time and have allowed a wOBA of .320. At the start of the game, the offense has the advantage of knowing who it’s going to be facing: The opposing starter, and which hand he throws with, is known hours in advance of the game, usually days. But once the game starts and relievers enter the picture, the information advantage swings back to the defense; when a manager makes a pitching change, he knows which three batters his reliever is going to face, and with short benches, the offense has little if any opportunity to make a countermove. This is why lefty relievers have the platoon advantage twice as often as lefty starters do.

As a result, the left-handed pitchers who have the most disproportionately lefty-heavy workloads are almost all high-volume relievers. So let’s zoom back out and focus on starting pitchers for a second.

This year, the average left-handed starter has thrown 20.6% of his pitches to left-handed hitters. The average right-handed starter has thrown 51.1% of his pitches to left-handed hitters. Here are the pitchers who, having been used predominantly out of the rotation this season, have faced the most disproportionately left-handed opponents, controlling for pitcher throwing hand:

It’s a mix. You’ve got some killer right-handed starters in there, but this group is a hodgepodge of good pitchers and innings eaters, and it’s a coin flip whether a pitcher on this list is actually better against righties than lefties.

Flipping the list upside-down, to the starters who face the most disproportionately right-handed lineups, is a little different:

Most of these pitchers actually do pitch left-handed hitters pretty well. Musgrove and Woods Richardson, for instance, have reverse splits. Skubal is nails against everyone, but his opponent wOBA is 35 points better against lefties than righties. Freeland has been horrendous overall, but he’s been almost average when you isolate the sample to same-handed batters. (Turnbull and Ortiz have split their seasons between the rotation and the bullpen, but I included them here just because.)

Playing matchups in the starting lineup is by no means an exact science; in some cases, the platoon advantage doesn’t make the top five most important pros or cons for playing or sitting a particular hitter. But Brown, relentlessly chucking four-seamers past one left-handed hitter after another, is not as much of an outlier as I’d originally thought.