He's throwing a what? The 'sweeper' is MLB's latest pitching weapon

Tune into baseball for long enough in 2022 and you’re almost assured to come across an unfamiliar term. The “sweeper” is the newest weapon being deployed against MLB hitters.

It is revitalizing the repertoires of some prominent pitchers and could have, um, sweeping implications for the seasons of the Los Angeles Dodgers and New York Yankees — two of the franchises most invested in it.

But what is a sweeper, exactly?

It’s a variation of breaking ball distinguished by horizontal movement — more across than up and down. Sweepers are essentially a subset of sliders, an endpoint on a spectrum that includes traditional sliders in the middle and hard, darting cutters on the other end.

The pitch is not new so much as it is increasingly prominent and intentional. And if teams are making a point of bending sliders into sweepers, maybe we should make a point of understanding the difference.

What makes a sweeper different than a slider?

If a style of pitch is going to become a pitch with its own name, one of the most prominent people who needs to be convinced is Harry Pavlidis. He founded the pitch classification service Pitch Info and oversees research and development for Baseball Prospectus.

Pitch Info has, this season, added sweeper as a distinct pitch category in addition to slider, curveball, cutter and so on. The difference, to Pavlidis?

“Movement,” he told Yahoo Sports via email this week. “The sweeper, as the name implies, sweeps laterally more than a conventional slider, which will tend to move but several inches less than the sweeper.”

Visually, it’s easy to catch on. Here’s a (very good) traditional slider from New York Yankees ace Gerrit Cole, courtesy the omnipresent PitchingNinja Twitter account.

And here’s Corey Kluber throwing what we are learning to call a sweeper.

See how its defining movement is veering off to the side instead of diving? If you were mimicking the shape of a traditional right-handed slider in your car, you’d power over a blind hill that slopes slightly to the left. If you were mimicking a sweeper, you’d take an exit ramp on the right and loop under the highway.

As Pavlidis points out, sweepers have been sweeping away batters in America and Japan for years. Yu Darvish is one of the most prominent pitchers who has deployed the pitch.

“We’ve seen it for years, it’s prevalent in NPB, and pitchers have been throwing it in MLB,” he said.

Kluber’s diabolical version helped him earn his two Cy Youngs in Cleveland. It was just particularly difficult to label. Many gave up and just called it a breaking ball. Others dubbed it a “slurve.” Pavlidis said the sweeper may be “nothing more than a rebrand of slurve.” That particular designation tended to carry a negative connotation, an accusation that a pitcher was struggling to separate two supposedly different pieces of his arsenal.

Not every variation on a pitch merits its own name. What makes the difference? For one, teams and pitchers themselves are adopting the term. And the league is noticeably adopting the pitch.

The Dodgers, who have added it or transformed existing pitches into it with Blake Treinen, Julio Urias and others, call the pitch a sweeper. The similarly enthusiastic Yankees had called it a “whirly” in 2021 before sweeper took hold in the industry.

Pavlidis also cited the increasing sophistication of pitch data that allows his group and the public at large to identify key differences that make a sweeper a sweeper, to the point where they can be separated out even when a pitcher also throws a regular slider.

One of those factors is the grip. This close-up view of Tampa Bay Rays starter Drew Rasmussen shows the transition from traditional slider to sweeper, what Pavlidis called “a full reorientation of the seams.”

This is how granular a revolution can be in baseball now. And it’s why sweeper’s definition and proliferation go hand in hand.

The change makes the sweeper grip two-seamed, a shift that gives the pitch its crucial, hitter-fooling qualities. That advanced information that helps identify the pitch can also help savvy evaluators and coaches identify and recreate those underlying qualities.

New Dodgers acquisition Andrew Heaney has added a
New Dodgers acquisition Andrew Heaney has added a "sweeper" and thrown it more than anyone else in baseball. (Photo by David Berding/Getty Images)

Why is the sweeper on the rise?

When the Los Angeles Dodgers — World Series favorites who often shop in the “future Hall of Famer” aisle — made homer-plagued Andrew Heaney the biggest addition to their starting rotation, every baseball nerd’s spidey sense went off. They must know they can make him better. At Baseball Prospectus, Michael Ajeto quickly and accurately predicted the plan.

Ditch the curveball. Add a sweeper that pairs better with the arm-side run of Heaney’s fastball.

His blistering start for the Dodgers — two starts, 10 1/3 innings, 16 strikeouts and only one unearned run — has made Heaney the face of a zeitgeist-y moment for the sweeper even though his is a pretty borderline example of the form.

Among the more textbook examples: Blue Jays starters Alek Manoah and Jose Berrios, Dodgers relievers like Treinen and Evan Phillips, and a parade of Yankees including Lucas Luetge and surprise star Nestor Cortes.

As Kluber has demonstrated so effectively for the past decade, sweepers and two-seam fastballs can look identical for much of their flight to the plate, then slay hitters by zigging or zagging in opposite directions. That concept is known as tunneling, and it’s a major part of the logic for adding a sweeper. So is “seam-shifted wake.” That daunting phrase is still a new frontier in baseball research with a lot of extremely technical questions we can’t yet fully answer, but the gist is this: Because of how balls thrown with that two-seamed grip interact with the air when spinning, sweepers move in ways that hitters’ eyes and brains don’t expect. It’s the same force involved in making sinkers and changeups difficult for hitters to square up.

At least in the public sphere, we’re still in the process of figuring out the impact of the sweeper. Does it help counteract a league of hitters that has worked to lock in on lifting the ball and hitting home runs? Is it perhaps an easier wipeout pitch to master without the use of sticky substances?

As front offices dig deeper into the numbers to find new advantages, there will be more realizations to come. May they all have names this catchy.