The Surge Of The Slider In The Pitch-Tracking Era

Image credit: Sandy Alcantara (Photo by Lachlan Cunningham/Getty Images)

Baseball is a game of adjustments, and one adjustment occurring on mounds across MLB has been a change in the distribution of fastballs and non-fastball pitch types.

Beginning in 2019, batters were nearly as likely to see a breaking or offspeed pitch as they were a fastball. That trend has only intensified in the four seasons since, to the point where roughly 47% of pitches thrown thus far in 2023 registered on pitch-tracking systems as two-seam or four-seam fastballs or sinkers.

While all non-fastball pitch types have increased in popularity, one pitch in particular has surpassed the others.

The slider is on a major upswing and has become much more common since 2008, the first season of the pitch-tracking era. This season, sliders are up 8.2 percentage points compared to 15 years ago.

The usage of cutters (+2.8), changeups (+1.0), curveballs (+0.8) and splitters (+0.5) is also up from 2008 levels, but none as dramatically as the slider.

To account for this uptick in breaking and offspeed pitch popularity, the fastball has been de-emphasized. Fastballs classified as four-seamers, two-seamers or sinkers are down 12.8 percentage points compared to 2008, meaning that there are nearly 13 fewer fastballs per 100 pitches than in the past.

Please note that the pitch distributions vary slightly depending on source. We are citing FanGraphs data, which incorporates MLB Statcast since 2015 and Pitch f/x before that.

In 2022, 20.8% of all pitches thrown were classified as sliders, the highest percentage of the pitch-tracking era and up dramatically even compared to 2021. The slider usage rate surged even higher in the early part of 2023.

Why has the slider become so popular? Part of the reason is because there are so many different varieties of the pitch, which makes it easier to tailor one type or the other to a pitcher’s individual characteristics.

“I think the primary property from my perspective is the adjustability that a slider allows while maintaining its effectiveness,” Brewers vice president of player development Cam Castro said. “Probably your two primary (slider) categories are bullets and sweepers, but even just to some lesser extent, some people would probably throw a cutter in the mix as well for kind of a third shape.

“And I think the biggest factor here is probably that there are just more versions of successful sliders than there are versions of successful curveballs.”

Castro identified several factors that go into choosing which type of slider might best fit a pitcher. Is his ideal plan of attack more east to west? Then he’s probably best suited for the sweeper slider that has become popular in recent years. If he works more north to south in the strike zone, then he might select a bullet slider, which breaks more vertically toward the feet of a hitter.

Take White Sox righthander Jonathan Cannon as an example. He works with both a cutter and slider with bullet spin. The pitch is effective for him for several reasons.

“He’s in the zone with it so often, he can throw it to both sides. He can expand up and down and he throws the living (heck) out of it at like 87 (miles per hour),” said John Ely, who is Cannon’s pitching coach at High-A Winston-Salem. “That velocity kind of helps it play up quite a bit, so that’s what you’re looking for with one of those: higher velocity, something that looks more like the fastball.”

Velocity is king these days, and that’s not just when it comes to fastballs. When possible, teams will opt for arsenals based more on power and less on finesse.

In 2022, the average fastball was thrown at 93.8 mph. The average curveball clocked in at 79.1 mph, meaning the separation between fastball and curveball was roughly 15 mph. The average slider, however, was thrown at 84.6 mph, which reduced the gap between it and the average fastball to about 9 mph.

The extra giddyup on sliders, which are designed to mirror a fastball out of the hand—Ely notes that the curveball is the only pitch that is released above a pitcher’s fingers, which makes it quickly recognizable—gives hitters even less time to decipher what’s coming and whether to swing.

Sliders offer a combination of velocity and deception that makes a properly executed version one of the toughest pitches to hit. For those reasons, breaking pitches in general are being thrown at a higher clip than at any point in history.

“Look at the New York Yankees, who have the highest fastball velocity in all of baseball on average, and from top to bottom,” Ely said.

“They also throw one of the lowest percentage of fastballs of any team, and they throw a higher percentage of breaking balls. Even with that (fastball velocity), that should tell you something: (the slider) is just a harder pitch to hit.”

The shift Ely referred to with the Yankees started after the 2020 season and is particularly dramatic. In 2020, the Yankees threw fastballs 38.7% of the time. The next year, that rate dropped to 31.5%, then to 29.7% in 2022. This season, just 28.3% of pitches thrown by Yankees pitches were fastballs.

That change has come with a corresponding increase in sliders. From 2020 until this year, the Yankees’ slider usage has jumped from 15.8% to 19.5%. That change is reflected up and down the organization, where sliders reign supreme among the system’s minor league pitchers.

When Will Warren, the Yankees’ top pitching prospect, came out of Southeastern Louisiana, his breaking ball was a curve. Once he became a pro, New York’s pitching development team altered his approach into one centered around two-seam fastballs and sweeper sliders.

“I think we do a pretty good job teaching guys how to spin the ball kind of depending on whatever secondary pitch we need to teach them,” Yankees pitching coordinator Sam Briend said. “(With Warren) it was like, ‘Man, it feels like you’re missing this in your arsenal. There’s a little bit of a hole here. You’ve got a lot of other really good things going for you . . . Let’s see if we can make this work as well.’”

The new approach has worked. In his short career, Warren has gotten whiffs and kept the ball on the ground. In his pro career he has struck out a batter per inning with a groundball rate north of 50%.

The allure of the slider boils down to the three V’s: velocity, versatility and variety. For those reasons, the pitch has become the weapon of choice for pitchers in the majors and minors, and it doesn’t look like it’s going to change any time soon.

Percentage point change from 2008 to 2023

SLIDERS

8.2% INCREASE

Cutters

2.8% INCREASE

Changeups

1.0% INCREASE

Curveballs

0.8% INCREASE

Splitters

0.5% INCREASE

Knuckleballs