The Sinker Continues To Be Optimized
Sinkers aren’t really in vogue these days. I mean, occasionally a cool GIF of a backdoor Aaron Nola two-seamer will pop up on Pitching Ninja, but to most of baseball, they’re just a type of fastball that needs to be thrown less often:
Sure enough, sinker usage across the league has been steadily decreasing for the past several years. But interestingly, we’ve seemed to have hit a plateau. You can interpret that as the league having successfully weeded out almost all of the bad and problematic sinkers; I certainly think that’s a valid interpretation, but I also think sinkers are experiencing a kind of revival. Did you know that this season, sinkers are returning much better results than four-seam fastballs? Me neither, until recently:
Well, well, well. How the turn tables. For most of the Statcast era, the league-average wOBA against sinkers has been higher than the league-average wOBA against four-seamers — not by a wide margin, mind you, but wide enough that front offices largely focused on optimizing their pitchers’ four-seamers, emphasizing the importance of backspin and locating up in the strike zone. The lowly sinker, meanwhile, became a relic of a past, a pitch that anachronistic organizations like the Pirates clung onto. That sinkers have overtaken four-seamers this season is a surprise, especially considering that offense is up. Whether due to the pitch clock having adverse effects on pitchers, the shift ban, or perhaps a livelier baseball, we haven’t seen a run-scoring environment like this since 2019. Almost all pitch types have seen an uptick in metrics like batting average and exit velocity against… except for the sinker.
So what’s going on? This isn’t the first time I’ve written about a sinker renaissance; in an article for FanGraphs last year, I noted two things: (1) that while the percentage of four-seamers thrown 95 miles per hour or above had doubled since 2018, the percentage of such sinkers quadrupled, and (2) that in 2022 alone, the average sinker added a half inch of vertical drop (which is a good thing — sinkers need to sink!). As a result, for the first time as of that writing, the run value per 100 sinkers was actually lower than the run value per 100 four-seamers. It didn’t last, but it became clear that the sinker was no longer an obviously inferior pitch. With the right pitcher and the right arsenal, it could still thrive.
But I’d be lying if I expected sinkers to be this ahead of four-seamers, this late into the season. To be fair, the gap is mostly explained by the sudden suckitude of the four-seamer, and I’m beginning to suspect that hitters have almost completely adjusted to the modern, high-octane fastball. That’s an article for next time, though. And again, what’s important is that the sinker hasn’t spiraled out of control, despite everything happening around it. The sinker has stood its ground. And it might be thanks to a simple optimization, one easy to overlook.
On a fundamental level, platoon splits exist because of how different pitches behave. Let’s imagine placing these pitches on a ‘platoon split spectrum.’ On one end, we have the platoon-adverse pitches, consisting of sliders and their varieties. These are very effective against same-handed hitters, but not so much against opposite-handed hitters. In the middle is the four-seam fastball, a neutral offering and the centerpiece of most pitchers’ arsenals. On the other end, we have the platoon-friendly pitches: changeups, splitters, and whatever Devin Williams throws. These are the pitchers’ usual weapons of choice against those pesky hitters of the opposite handedness.
But what about the in-between pitches? There can be disagreements on where exactly they fall on the platoon split spectrum. In general, though, you can confidently say that cutters are between ‘neutral’ and ‘platoon-friendly’: They’re effective against opposite-handed hitters, but because they still move in the direction of their swings, they nonetheless present an opportunity to do damage. You can also confidently say that curveballs are between ‘neutral’ and ‘platoon-adverse’, with their exact placement on the spectrum depending on their shape (a 12–6 curveball is more neutral, platoon-wise, than a slurve.)
We don’t often think about sinkers in this regard. But they too are impacted by batter-pitcher matchups — maybe even more than you think. There’s a reason why right-handed hitters hit more grounders against right-handed pitchers than against left-handed pitchers, and vice versa. Or in terms of batted ball data, when righty hitters swing and make contact against righty pitchers’ sinkers, they average lower launch angles than they do against lefty pitchers’ sinkers. This disparity adds up: In 2021, for example, righty-on-righty sinkers returned a .341 wOBA on contact, whereas righty-on-lefty sinkers returned a .390 wOBA. On our platoon split spectrum, sinkers aren’t just standing smack-dab in between sliders and four-seam fastballs; they’re practically cuddling with sliders and giving four-seamers the cold shoulder.
The sinker is far from a neutral pitch. But it’s surprisingly taken the league, and myself included, a long time to realize this. Maybe you already knew, in which case, you have my respect! Either way, I think we can appreciate what all this has been leading up to:
This is the optimization I alluded to earlier. It’s subtle, it isn’t terribly exciting, and it won’t make headlines — but it’s absolutely the right thing to do. It’s as simple as going up to your pitcher and saying, “Hey, your sinker is good, but you should throw it less often against lefties.” The uptick in righty-on-righty sinkers hasn’t been too significant this season, but look how far it’s risen over the last several years. This isn’t just a renaissance; it’s a revolution, a quiet one at that. For comparison, the rate of righty-on-righty sliders has remained stagnant for as long as we’ve had granular pitch data, capping out at around 70%. Realistically, that seems like the ceiling for sinkers as well.
And lest we forget about them, here’s the same graph but for lefty pitchers:
There’s more of a fluctuation here, most likely because lefty-on-lefty matchups tend to be rare, reducing sample sizes. But the overall trend is identical. Even though lefty pitchers face hitters of the opposite handedness far more often, they’re still finding ways to sneak in sinkers against fellow lefties. Considering how sensitive baseball is to pitcher-batter matchups, it’s surprising that it’s taken so long for such optimization to really take off. But no matter: With the technology and information available, the sinker has quickly caught up to the competition. It took decades for slider usages to end up where they are now. It’s taken maybe six or seven years for sinker usage to undergo the same transformations.
It’s a culmination of everything mentioned so far — faster velocities, sharper movement, and optimized usage — that’s likely what’s fueling the sinker’s surprising dominance in 2023. Sweepers are all the rage these days, but I dunno, I find sinkers being the fastball of today’s game far more fascinating. Now there’s an underdog you can root for.
