A Sweeping Sensation: What We Know About Baseball’s Hot New Pitch

As players reported to Spring Training this year, the headline “Pitcher X has added a sweeper” feels like it replaced the “best shape of his life” mantra. New pitches were unveiled in early February bullpens from a wide variety of pitchers, ranging from Zack Wheeler, to Joe Ryan, or even Ryan Tepera. This year, all sorts of pitchers are coming into 2023 with this new pitch.

While the sweeper started to become mainstream last year, it seems to be trending toward a new level of usage in 2023. Last month, it was announced that the sweeper would be its own unique pitch classification on Baseball Savant’s website, giving it a big step forward for public understanding and analysis.

The big change for this year is that we have added the "Sweeper" slider and "Slurve" as discrete pitch types. We'll be reviewing career data for all pitchers and will be gradually making appropriate updates in the coming weeks and months…

— MLBPitchClass (@MLBPitchClass) February 23, 2023

And the sweeper is already taking center stage this year; Shohei Ohtani struck out Mike Trout on a filthy sweeper to win the World Baseball Classic earlier this month.

Congrats Team Japan! 🇯🇵 pic.twitter.com/6JDpOM4XGa

— Rob Friedman (@PitchingNinja) March 22, 2023

Ohtani threw more sweepers than anyone in 2022. One of the early adopters of the pitch, Corey Kluber, can make his sweeper look like a frisbee.

Corey Kluber, Sweeper with 22 inches of horizontal break. pic.twitter.com/dFV1Hj2WrX

— Rob Friedman (@PitchingNinja) April 16, 2022

It may not look entirely like a new type of pitch movement, but the pitch design breakthrough on sweepers is bringing new light to why this movement profile can be devastating to hitters.

 

What Exactly Is the Sweeper?

 

As for a true definition of the pitch, Dan Aucoin of Driveline (now with the Phillies doing R&D) outlines how Driveline classified sweepers in 2021: 77mph, 6.5 inches of glove-side movement after 40ft of ball flight, and -2 inches of depth after 40ft of ball flight. This 2021 Fangraphs chart contrasting pitch types by movement depicts how the sweeper fits in with other pitches:

The sweeper fits the vertical movement of the slider and shares the horizontal movement characteristics of curveballs and big sliders (simply, extra “sweep”). The velocity of the pitch rests in between sliders and curveballs as well: the 2022 league average sweeper was 80.2mph, compared to 84.2mph on sliders and 79.0mph on curveballs. A great example of the differences between each pitch type is Chris Bassitt, who throws all three.

 

 

The sweeper is thrown slower than the slider but has that extra bite that causes Schwarber to swing through it and walk back to the dugout confused.

One who isn’t fully up-to-date with the sweeper may ask: “How is this different than a slurve?”

Traditionally, calling a breaking pitch a slurve often meant that a pitcher struggled to distinguish their breaking ball from a curveball and a slider. The sweeper is a new version that is actually a step forward, rather than a step back. While yes, they do look similar, the sweeper is a development in pitch design that makes the sweeper out to be more than meets the eye.

 

The Magic Behind the Sweeper

 

I say “magic” behind the sweeper, but it really is just physics that makes the pitch unique (although these pitchers may look like magicians). In simple terms, the sweeper moves more than the spin, velocity, and pitch grip suggests, which is a calculation done through the StatCast cameras in MLB ballparks. This additional movement is difficult to anticipate, hence why it has become an effective tool as of late.

In more complex terms, this additional movement is caused by changes in the Magnus effect of the baseball. The Magnus effect, in this situation, is the concept that the ball moves based on the pitcher’s grip of the ball and how their fingers apply pressure upon release (for more on finger pressure, take a look at Alex Fast’s recent article).

Other Magnus effect examples that may make sense are the curve on a tennis ball when it’s hit or the slice of a golf ball that I just hit 50 yards out of bounds (why I’m writing about baseball!). The spin on a ball creates a wake in the air as it cuts through the air, but it is based on how the motion of the ball began (e.g. throwing a pitch, hitting a golf ball, etc.). The wake can also be visualized through what happens to a body of water when an object moves through it.

However, because a baseball has lifted seams on it, there can be some irregular movement in flight. The seams, when thrown in certain movement profiles, can create enough turbulence in the air which, in turn, can allow the ball to have free movement. This is known as the non-Magnus effect. Essentially, this means that the ball can move in ways that cannot be anticipated by just watching the release.

This sensation is called seam-shifted wake (SSW). Every pitch has at least a little bit of SSW, but smaller differences between spin-based and observed movement will not dramatically change how a batter reacts to a pitch. Sweepers, however, have a large deviation between the two, which makes them an effective tool for missing bats. Other pitches that can see significant benefits from SSW are sinkers and offspeed pitches (e.g. changeups).

One of the easiest ways to identify seam-shifted wake is through Baseball Savant’s spin profiles on their player pages, which show the spin-based and observed movement of a pitch. Pitches that have high amounts of SSW can be noticed through large deviations in their spin-based and observed movement. Taking Ohtani as an example again, the sweeper stands out in his arsenal.

While the fastball, cutter, slider, and curveball all show slight deviations in their movement profile, the sweeper, sinker, and split-finger all show significant differences between their spin-based and observed movement. These pitches all have slight amounts of SSW, but the sweeper, sinker, and split-finger are pitches that utilize this phenomenon specifically to get results.

 

Who’s Throwing The Pitch?

 

While guys like Corey Kluber and Adam Ottavino have been throwing the pitch for a while, recent research has inspired many others to adopt the pitch. Baseball Savant has retroactively attributed sweepers to pitchers from previous years, which tells us that the pitch is just making its way into the league now. One caveat to the sweeper data is that a lot of the sweepers are classified based on pitchers outright stating that they are throwing the pitch, but some can be identified through movement as well.