Reports of the Sinker’s Death Have Been Exaggerated

In 2018, an article by FanGraphs alum Travis Sawchik came with an ominous title: “Go See the Two-Seamer Before It’s Gone.” His instruction alluded to a still-ongoing trend within MLB, whereby numerous pitchers abandon their two-seamers and sinkers in favor of high-spin four-seamers thrown up in the zone. Its impetus boils down to a couple key developments. For one, teams and pitchers wanted to counter batters who adjusted their swing planes to elevate low pitches. They also realized that high fastballs are useful at inducing whiffs, regardless of batters’ tendencies. Furthermore, those fastballs paired well with the breaking ball shapes and locations teams began to covet around the same time.

All in all, the stage was set for a league-wide revolution. You’ve read the stories of how Gerrit Cole and Tyler Glasnow blossomed into superstars using high fastballs. Conversely, you’ve heard the story of how forcing the sinker upon Chris Archer aggravated his struggles. You might have also encountered stories connecting this trend to the recent uptick in strikeouts. The validity of these reports aside, they helped cement a narrative: the four-seamer was in, and the sinker was out.

Three years later, the league doesn’t seem to have veered away from it. Pitchers have located 20% of four-seam fastballs in the upper-third of the zone this season, the highest rate of the Pitch Tracking era (2008 onwards). Meanwhile, two-seamer/sinker usage is the lowest it’s ever been.

But that doesn’t mean the sinker has stopped dead in its tracks. If anything, the pitch has become better in the aggregate, a result of mediocre sinkers being dropped and quality ones being retained. The so-called demise of the sinker describes its waning popularity, not development. Below, we can see an example of the latter. I plotted the percentage of four-seamers thrown 95 mph or higher since 2008, then compared it with the percentage of two-seamers/sinkers thrown 95 mph or higher. There’s an interesting difference:

For the most part, the rise in 95-mph four-seamers has been gradual and linear. As for sinkers, however? You could almost fit an exponential curve! This is a dramatic change that one would miss when looking at only average velocity:

It seems like the distribution of sinker usage by velocity is skewed more to the left than in years past; the mean hasn’t budged, but the extremes have. Part of that might be pitchers with below-average sinker velocities using the pitch less, reasoning that they would benefit from other offerings. And while it’s become common for flamethrowers to work in more four-seamers, what if the opposite is happening? Consider Yankees reliever Jonathan Loaisiga, who has been increasingly reliant on his sinker despite a robust velocity:

In Loaisiga’s case, the increased sinker usage is an optimization. Although his four-seamer is multiple ticks above the league average, the lack of movement translated to hard contact in the beginning of his career. Since endorsing the sinker in 2020, Loaisiga has limited opposing batters to a hard-hit rate of 24.5%, and there’s even been a minor yet vocal effort to send him to this year’s All-Star Game. It’s possible that he’s an exception in terms of magnitude, but regardless, his evolution is proof that the sinker is hardly dead. Rather, it can thrive under the right circumstances.

That being said, I’m not sure if higher sinker velocity correlates to better results, whether that be in terms of wOBA or Run Value. It’s extremely difficult to untangle the relationships between velocity and variables like movement and location, not to mention other pitches. At a glance, there’s no significant relationship between sinker velocity and xwOBA allowed (r^2 = 0.04); in this world, there exists both Jonathan Loaisiga (97.8 mph, .210 xwOBA) and Miguel Castro (98.3 mph, .501 xwOBA). The difference between them? That’s perhaps for an article in the near future.

A turbo sinker itself is a bit of a contradiction. Velocity on a four-seamer is useful not only because it carves out a differential between a pitcher’s secondary pitches, but also because it supplies extra spin, and therefore more ride. Add velocity to a sinker, though, and you get… less sink. It’s not helping with horizontal movement, either.

Based on this, throwing both pitches effectively seems impossible; one benefits from added spin, but one doesn’t, so what is a pitcher supposed to do? That so many have moved on from the sinker to escape this conundrum is no surprise. But in 2021, some of the game’s best pitchers are relying on a combination of four-seamers and sinkers:

These aces aren’t slipping in a sinker once in a while; it’s a legitimate part of their repertoire that doesn’t bog them down. But as expected, none of the four possess exceptional four-seamer ride or sinker drop; the two pitches work against each other to create middling movement profiles. So how do they manage to achieve success? As in most cases, the answer is that each pitcher’s method is tailor-made. Lynn throws three types of fastballs — four-seamers, sinkers, and cutters — from the same arm slot, making it a hassle for hitters to pick up on any one fastball. Alcantara employs a similar strategy, but with changeups instead of cutters. Woodruff gets ahead in the count with sinkers, then switches to four-seamers once batters are behind. Walker, who threw his sinker just 0.8% of the time in two-strike counts last year, has bumped that rate to 20.5%.

Besides these examples, there’s maybe reason to expect sinkers will experience a small resurgence. Fastball spin rates tumbled as MLB announced its draconian measures against foreign substances, and starting this week, umpires are inspecting pitchers during games. If four-seamers are no longer as effective for some pitchers, might they be motivated to incorporate (or re-incorporate) a sinker that doesn’t mind a decline in spin rate?

It’s unlikely we’ll see a mass exodus from four-seamers to sinkers, but the risk involved is minimal enough that a few pitchers could take a chance. For instance, updating a bar graph within Sawchik’s article, here’s how hitters have performed against four-seamers up compared to two-seamers/sinkers down:

While the league’s output against high fastballs has essentially stagnated, its output against sinkers this and last season is down. There’s no doubt some survivorship bias baked into the numbers of 2020–21, but that’s sort of the point; if they wanted to, skilled pitchers capable of commanding a plus sinker may have a better chance at success than in years past. Low sinkers are also allowing lower xwOBA on contact compared to high fastballs, though the caveat here is that the batters make less contact with the latter. Still, sinkers: They ain’t too shabby!

Finally, the concept of seam-shifted wake has also become relevant since Sawchik’s article. I saved the discussion for last because it’s an enigma; we don’t know what kind of grip grants pitchers access to its mysterious power. We at least know, however, that it’s beneficial. Research from Driveline Baseball has shown that sinkers with greater seam-shifted wake effects outperform their expected run values, and a Pitcher List article demonstrated a “relatively strong relationship” between launch angle and the absolute value of spin axis deviation. If teams figure out how to develop seam-shifting sinkers from the get-go, that’s one additional reason for sinkers to come back in vogue.

Teams still value the vertically-oriented fastball shape, and for good reason, as it’s proven to generate whiffs up in the zone and pair well with power breakers, providing its wielder a decent floor. Sinkers help with contact management, but you probably know how volatile results on balls in play are. Yet advances in pitch design have also helped pitchers to optimize their sinkers. Articles once decried the death of the two-seamer/sinker; in reality, it’s never gone away. Sure, sinker usage is at an all-time low, but its viability is not. And as MLB faces a future without foreign substances, an endangered pitch offers a potential respite.