The Sweeper Is MLB’s Trendiest Pitch, But It’s Not Entirely New

The slider-curve hybrid has been around for more than 50 years. Corey Kluber won two Cy Youngs with it. So why is it just catching on now?

Welcome to The Opener, where every weekday morning during the regular season you’ll get a fresh, topical story to start your day from one of SI.com’s MLB writers.

ST. PETERSBURG, Fla. — Corey Kluber has long said that his breaking ball resists classification. It’s not a curve. It’s not a slider. It’s just his breaking ball—the pitch that helped him win the Cy Young in 2014 and ’17, and that still bedevils hitters today, with far more horizontal break than a traditional slider yet less drop than a traditional curve.

But this year has brought something new. The hottest trend in pitch design right now is a breaking ball that can look a lot like Kluber’s: a slider with extra horizontal motion. All that side-to-side break invites people to call the pitch a “sweeper.” (Though some clubs have developed their own variations: The Yankees, for instance, call theirs the “whirly,” as detailed by Lindsey Adler at The Athletic.) There are plenty of individual pitchers who have been experimenting over the last few years, trying to get more break on their sliders. But this spring has seen a dramatic uptick—particularly among savvier teams, which have been using data to craft sweepers on a bigger, organizational level. You can see the results across baseball. And that’s prompted those in charge of classification to call this a distinct pitch: Search the PitchInfo data hosted at Baseball Prospectus, or look at material from Driveline Baseball, and you’ll now see a sweeper listed on its own, separate from a slider or a curveball.

Near the top of the leaderboard for most sweepers thrown so far this year? Of course: Kluber.

Scott Audette/AP

After years of telling people that his breaking ball really is not a curveball or a slider, does an official classification now feel somewhat like validation? Is it nice to be ahead of the curve (or, ahem, in front of the sweep)? Does he even think of his breaking ball as a sweeper in the first place?

“Not necessarily.”

The Rays pitcher gets why someone would ask. And he knows that his pitch really can look like the sweeper that has become so popular. But for Kluber—who perhaps did more with it earlier than anyone else—it’s still just his breaking ball.

“Throwing it for so long, with repetition and experimenting with what works and what doesn't, I think I've kind of developed a feel to make it do different things,” he says. “Sometimes I can make it a little more horizontal. Sometimes a little more vertical. But I wouldn't say that the intent is to make it a quote, unquote, sweeper.”

All of this underscores some of the natural trickiness of classifying pitches: Yes, you’re hearing about the sweeper as a new pitch this year, and it is new to pitch classification leaderboards. There are more players experimenting with their breaking balls to make them more effective in this specific way. But all of this can be more of a spectrum than a binary. And the fact that it’s increasingly visible doesn’t mean it’s brand new. (“Slurve” was first used to describe a pitch between a slider and a curve all the way back in 1970, according to the Dickson Baseball Dictionary, even if the term doesn’t have the sexy, forward-thinking connotation that “sweeper” does.) Rather, it’s an example of how pitch design can evolve gradually over time, and how much that process can accelerate with new data and technology. Statcast didn’t exist when Kluber won his first Cy Young in 2014. Now? There’s increasingly granular information about every single pitch. That makes it easier to analyze the horizontal movement that can determine just where a slider ends and a sweeper begins. It also makes it easier for teams to learn in exactly which situations that kind of break might be most effective, which leads to pitchers knowing when to throw it more, which … leads to the kind of popularity that allows people to see it as its own pitch.

“There’s been some information out there that moving the ball horizontally has led to more swing-and-miss and more strikeouts,” says Tampa Bay pitcher Brooks Raley, who developed a sweeper during his time with the Astros and credits it for helping him draw interest in free agency this winter from the Rays. “I think that’s why the game has adapted to that. Especially when hitters have made adjustments on the top of the strike zone and the bottom … You’re seeing a lot more pitchers go left and right.”

Raley is just one of the Rays pitchers who has joined Kluber in throwing the sweeper. Another is Drew Rasmussen—one of the few pitchers in the game who has relied on the pitch this year even more than Kluber. For him, it’s entirely new. Tampa Bay pitching coach Kyle Snyder approached him in spring training about making his old, textbook slider into a sweeper, and together, they’ve worked on getting it there.

“Basically, all we've done is change the grip a little bit, but not really how I throw it a whole lot,” explains Rasmussen. “And then just shifting seams a hair has created a little bit more action to it.”

Per PitchInfo, his slider last year averaged less than two inches of horizontal movement. His sweeper now averages more than triple that.

Watch MLB games online all season long with fuboTV: Start with a 7-day free trial!

He thinks of it as something entirely separate from his old slider. Which can be one of the benefits of establishing a new classification: When something is differentiated by name, it’s easier to build out a more specific idea of what it should look like.

Yet for Kluber, who has long resisted labels here, that’s exactly the issue. When he thinks of a curve, he pictures one specific kind of motion; when he thinks of a slider, he pictures another; now, when he thinks of a sweeper, he pictures yet another. Maybe everyone else has found something to call his signature pitch. To him, it’s most effective when he just lets it go, no classification.

“I think I get in my own way,” Kluber says. “I start trying to do what, in my head, I imagine what that pitch looks like—instead of what my intent is.”

Yet, amid all of that, this season has brought one area where he does have to classify his breaking ball—PitchCom, the new technology being tried out by some clubs, including the Rays. The system allows a team to call pitches with a recording played at the press of a button rather than a sign given visually. Which means that Kluber’s backstop has to choose whether the pitcher will hear slider or curveball or sweeper when he wants a breaking ball.

They have to pick one, and so far, they’ve usually gone with slider. But Kluber still thinks of it just as his breaking ball—no matter how sweepy or curvy or slidey it might be.

So: Any thought of changing the PitchCom settings? Incorporating a Kluberball button, perhaps?

“I think you can customize it,” he says with a smile. “But that seems like a lot of work.”

Sports Illustrated may receive compensation for some links to products and services on this website.