Thinking About Sinking

Last week, Justin Choi wrote a fascinating article about sinkers. You should read it, because Justin’s stuff is great, but I’m going to summarize it here because I want to riff on it a little bit. In essence, Justin pointed out what we all kind of knew but didn’t talk about much: sinkers are much better against same-handed batters. Teams have caught on, and they’re changing usage accordingly.

Here’s a great chart from that article: the percentage of all right-handed sinkers that are thrown to right-handed batters:

That’s pretty straightforward: pitchers are increasingly using sinkers only when they have the platoon advantage. Here’s another way of looking at it: the percentage of sinkers among all pitches thrown by righties to lefties, league-wide:

In plain English, pitchers have stopped throwing sinkers when they’re faced with opposite-handed batters. Meanwhile, they’re throwing right/right sinkers as frequently as ever:

Those two charts hardly look like the same pitch, and in fact they aren’t really. Righty pitchers are actually playing two slightly different games: they’re pitching to same-handed batters and separately pitching to opposite-handed hitters. The object of both games is to get the batter out, so it’s not like the games are that different, but it’s inconceivable that the same pitches would be best against both sides.

Let’s delve a little deeper into why sinkers merit this huge split usage. At a basic level, the argument is pretty simple. Take a look at groundball rate, wOBA on contact, chase rate, and whiff rate for sinkers thrown by right-handed pitchers in 2023, split by handedness of opposing batters:

More grounders and the resulting lower production on contact are the key differences here. As a point of comparison for how platoon-sensitive a pitch is, here’s the same chart for four-seam fastballs:

Four-seamers allow louder contact than sinkers and make up for it by missing more bats. But they allow similar production on contact regardless of the handedness of the batter.

To be fair, there are some selection effects here. Some of the sinkers thrown by righties against lefties are from pitchers who simply have nothing better to throw, and those guys tend to be bad. Both effects shrink if we look at individual pitchers and compare their results against lefties and righties. But the overall shape of the effect is clear. Unless you’re throwing a particular subset of sinker, as Cam Levy wrote about earlier this year, the platoon effect is hugely important.

The general idea here is simple: throw your best pitches often. What’s changed is how teams and pitchers are deciding what’s best. To get an example of this, I decided to use two teams as a case study. First, we’ve got the 2014 Pirates, the foremost example of the mid-2010s sinker trend. Their starters threw sinkers a whopping 43.4% of the time. We’ll also look at the 2022 Phillies, whose starters threw the most sinkers in baseball last year (28.5%). The way these two teams use their pitches is emblematic of the era each is from.

First, take a look at Pittsburgh’s starters from that year:

This group is all over the place when it comes to pitch usage, but broadly speaking, they were equal opportunity sinker throwers. Morton and Locke threw theirs much more frequently with the platoon advantage, but the rest of the crew didn’t really. In aggregate, Pirates hurlers decreased their sinker usage by only five percentage points when they didn’t have the platoon advantage.

How’d that work for them? Not particularly well:

When thrown to same-handed batters, Pirates sinkers were phenomenally effective, allowing a wOBA around .330 when the opposition put the ball in play. When thrown to opposite-handed pitchers, those sinkers were stinkers, allowing a wOBA of .379. Single-pitch platoon splits are tremendously noisy, so don’t read too much into any single pitcher’s line, but the broad point remains: these sinkers got creamed when hitters had the handedness edge. And this wasn’t a bad pitching staff; they were second in the majors in WAR.

That was the sinker-iest team of 2014, perhaps the sinker-iest year in baseball history. How does the 2022 version compare? Things have changed, and yet some practices remain the same. Here are the Phillies starters who threw sinkers last year (excluding opener Cristopher Sánchez):

Right away, you can see that usage patterns have changed. Did you see those graphs up at the top of the article? The Phillies had a lot to do with those. How’d they fare with their approach? Fairly well:

Bailey Falter is weird. Even accounting for that, though, the change in pattern is clear. Most Phillies starters threw far more sinkers when facing same-handed batters than they did when opposite-handed batters were up. Like their time-shifted Pirates counterparts, they ran a higher groundball rate and allowed a lower wOBA on contact against same-handed hitters. Weighted by number of sinkers thrown, Phillies pitchers had a 9.5% groundball edge and 27-point wOBACON edge when they had the platoon advantage. They leaned into that gap by ditching sinkers when they weren’t set up to succeed.

I’m not sure you’d think of the Phillies as a sinker-first pitching staff. I think of them more as a top-heavy pitching staff than anything else; Nola, Wheeler, and Suárez are excellent, and the rest of the rotation is sketchy. But they threw more sinkers than four-seamers, and got better results with them. In fact, they got the best production on their sinkers out of any team in baseball. It might not lead to a bestselling book anytime soon, but just because sinkers are out of fashion doesn’t mean teams aren’t using them well.

As Justin mentioned in his article, this kind of handedness optimization is sweeping across baseball, and with good reason. You have to fill that gap in usage somehow — changeups, four-seamers, cutters, whatever your favorite neutral option is — but it’s a switch worth making. Sinkers are excellent pitches, particularly if you use them right, and the league seems to be getting better at just that. It feels weird to treat a fastball like a slider and put it in your back pocket against opposite-handed hitters, but you can’t fight the math, so you might as well join it.