Go See the Two-Seamer Before It’s Gone

Baseball goes through its trends like about any other industry. Just about everything goes through a constant flow of peaks ebbing to lulls and then back to peaks agains.

Pitch types, for example, go through cycles of popularity. The curveball was out of fashion and now it is back. There are years where different pitches are more prominent than others. Different pitches do different things. They dart left, right, down, and appear to rise. They have different shapes, breaking in different depths. Their usage is tied to the swing plane, philosophies, and ball properties of the day.

You are probably aware that the two-seam/sinker has fallen out of favor in recent years.

While the fastball is generally losing market share in favor of breaking pitches, the four-seam fastball has actually enjoyed an uptick in popularity in recent years as pitchers take advantage of their newly quantified spin rates to better get over the swing planes of batters, who have adapted to hammer the low pitch, as Jeff Sullivan observed prior to last season.

In 2010, two-seam/sinker usage was at its peak of 22.5%, according to Pitch Info data. Four-seam fastball usage was at a pitch-tracking-era low of 34.8%. This season, two-seam/sinker usage is at a pitch-tracking-era low of 17.8%, its sixth consecutive year of decline. Four-seam usage is up to 37.6%.

Additionally, more teams — teams like the Astros, Blue Jays, and Yankees — seem interested in adding spin instead of subtracting it. The Pirates represent an outlier for their efforts in targeting and teaching low spin.

Over the past three years, no team has exceeded a 50% ground-ball rate, after the Pirates averaged a mark about 50% from 2013 to -15 — the product of a two-seam-heavy philosophy intended to induce grounders into defensive shifts. While shifts are still popular, teams seem less focused on trying to create ground balls off the mound.

Maybe the two-seamer will be back in a few years after batters find a way to combat velocity up in the zone. Maybe you don’t have to worry about the pitch going extinct just quite yet. There’s always going to be a use for the two-seamer. There will always be a place for a Brandon Webb-level movement on a two-seam fastball. The come-back, two-seamer will always be a weapon. It is always important to play to an individual pitcher’s strengths. But at a macro-, MLB-wide level this does feel a little different.

For starters, batters have become better low-ball hitters, so the core pitching axiom of “keeping the ball down” isn’t as effective as it was a generation ago. There has been a fundamental shift in thinking about how to hit and swing. More and more, the two-seam plane is lining up with swing paths.

Moreover, technology advances have allowed pitchers to better understand the movement of their pitches. They know that, with a high-spin fastball, they have a better chance of recording whiffs at the top of the zone or just above it. While we should perhaps anticipate batters to adapt to some degree to the high pitch, what if the high fastball keeps gaining velocity and spin?

As velocity increases, so does spin, and the more spin a ball has, the more it resists gravity and appears to rise. While the addition of spin to a four-seam fastball is good for that pitch, it adds upwards vertical movement to a sinker, creating the opposite of the intended effect.

As long as pitchers are becoming bigger and stronger, and as long as bullpens absorb more and more innings, velocity and spin should continue to increase. Fastball velocity is at record highs again this season: 93.3 mph for starters and 94.4 mph for relievers. Spin is increasing for both four- and two-seam fastballs. Four-seam spin is averaging 2,263 rpm this season, up from 2,255 last season and 2,238 in 2015. Two-seam spin has averaged 2,169 rpm each of the past two seasons, up from 2,157 in 2016 and 2,138 in 2015.

So while some pitchers might still have excellent natural sinkers, or develop ways to reduce spin via grip or technique, the global trend is that fastballs are adding spin, which should generally aid the four-seamer. Teams and pitchers are trading in four-seamers for two-seamers.

What’s interesting is that batters continue to have a better xwOBA against two-seamers down (.350 this season and .337 last season) than four-seamers located up (.328 this season and .313 last season), according to Baseball Savant data. While batters are perhaps already beginning to adapt against the high fastball, they’re not suffering in performance against the two-seamer.

Maybe the sinker will have its day again, or perhaps this time is different for the two-seamer. Many things are recycled in baseball, but not everything is. Maybe, with hitting instruction having been turned upside down, the sinker will never get its market share back. If that’s the case, go out and see the sinker before it’s gone.