Saturday Study Hall, Vol. 4
What is induced vertical break, why does it matter and which Royals boast the best iVB metrics?
Saturday Study Hall is a biweekly series defining advanced stats, data and analytics to investigate how they impact the Royals.
This new era of pitch tracking brings a wealth of data and information we could’ve only dreamed about a decade ago. From the fundamental (velocity) to the advanced (spin rate and movement), we have an infinitely better grasp on what separates one pitcher’s arsenal from another’s.
Our own Kris Bubic and JP Sears of the Athletics, both left-handers, average 92.2 MPH with their four-seam fastballs this season. Yet Bubic’s heater returns a 105 FanGraphs Stuff+ while Sears’ grades out at a ghastly 80. What’s the cause of such a massive gap in pitch quality at the same velocity?
Stuff+ (which you can learn more about on FanGraphs) isn’t the topic for today. It’s a pitch model (actually, there are several, including FanGraphs’ version created by Eno Sarris and TJStats’ version that I often cite) that accounts for a variety of criteria and boils it down to one easily digestible number, inclusive of data points like velocity, release point, spin rate and today’s focus: movement.
We’re continuing our Saturday Study Hall series — a biweekly exercise — with a specific measurement of a pitch’s movement called induced vertical break, or iVB. It’s an important factor (though probably not the only reason) Bubic’s four-seamer dusts Sears’ in the stuff department.
If you’re familiar with baseball parlance in the slightest, you know (or can guess) what vertical break refers to — the downward movement of a pitch expressed in inches. The y-axis of the below illustration charts the vertical movement of every pitch Seth Lugo threw in 2024. You can see how fastballs (four-seamer, sinker, cutter) differ greatly in their vertical break compared to offspeed offerings (changeups and splitters) and breaking pitches (sliders, slurves, sweepers and curveballs).
While the 60+ inch break on Lugo’s curveball seems superhuman, even alien, here on planet Earth we have what’s called gravity. Every pitch, after leaving a pitcher’s hand, will succumb to the effects of gravity and be pulled downward.
What iVB attempts to do, as opposed to standard vertical break, is remove gravity from the equation to focus only on a pitch’s movement caused by effects like spin. Similar to many other “advanced” data and metrics, what sounds complicated on the surface is actually quite simple — removing gravity as a variable to get a clearer picture of a pitcher’s talent/skill/technique in creating movement.
To help show the difference, here’s Lugo’s induced break movement profile from last year, courtesy of Baseball Savant. (Note, the above is from the catcher’s POV, below is from the pitcher’s POV.)
It’s critical to note, as you’re likely aware, there’s no such thing as a “rising” fastball. Instead, the elite iVB fastballs across the game produce a rising effect, dropping less and holding their plane better than an average fastball — but still dropping nonetheless.
While iVB is typically used to measure the rising effect or “ride” of fastballs, it’s similarly useful when comparing breaking balls as it removes the time-sensitive nature of gravity. Simply put, a slower breaker takes longer to get to the plate, allowing the effects of gravity to act for a longer period of time versus a harder breaker getting to the plate quicker.
Take Lugo’s curveball for example. While he’s not a velocity chaser, he did throw his curve relatively hard at 78.2 MPH in 2024, top half of the league among qualifiers. The pitch delivered 58 inches of vertical drop, 52nd in MLB, per Baseball Savant. But its -14.5 inches iVB ranked 30th, displaying Lugo’s ability to spin and manipulate the baseball without needing gravity to “pull” the pitch downward — it’s no surprise his curveball ranked first in the league in spin rate at 3,285 average RPM. It’s also no shocker to see that combination of velo and spin propelled the pitch to a 107 FG Stuff+, seventh-best in MLB for its pitch type.
Royals Pitchers and iVB
As mentioned, iVB is most often used to judge four-seam fastballs, so that’s where we’ll focus today’s case study on Kansas City’s 2025 pitching staff. To help provide a baseline, let’s also look at MLB’s leaders.
One last note you should know when comparing iVB averages: Arm angle plays a pretty crucial role here. Over-the-top arm slots are easier for generating backspin compared to lower slots — just hold a baseball in your hand and replicate a couple different angles and you’ll see why.
When your arm is over the top, your hand is naturally behind the baseball and able to spin the four seams perpendicular to the ground. From a three-quarters angle, the baseball is naturally tilted, making it tougher to generate direct backspin.
Physics, man.
2025 MLB Four-Seam Fastball iVB Leaders (min. 50)
Alex Vesia (LAD), 21.7 inches
Triston McKenzie (CLE), 20.7 inches
Nick Pivetta (SD), 20.5 inches
Jeremiah Estrada (SD), 20.4 inches
Yuki Matsui (SD), 20.2 inches
Jack Dreyer (LAD), 20 inches
Tyler Anderson (LAA), 20 inches
Justin Wilson (BOS), 19.9 inches
Colin Poche (WSH), 19.8 inches
Landon Knack (LAD), 19.8 inches
Hmm, I wonder what the Padres and Dodgers value in their pitching staff!
2025 Royals Four-Seam Fastball iVB Leaders (min. 25)
I’ve included arm angle here, too, for a bit of added context.
Kris Bubic, 18.7 inches, 39.9 degrees
Michael Wacha, 18.6 inches, 51.4 degrees
Carlos Estevez, 17.7 inches, 40.8 degrees
Hunter Harvey, 17.6 inches, 45.7 degrees
Cole Ragans, 17.2 inches, 39.4 degrees
Sam Long, 17.1 inches, 50.7 degrees
Chris Stratton, 16.9 inches, 35.7 degrees
Steven Cruz, 16.8 inches, 33.5 degrees
Michael Lorenzen, 16.6 inches, 44.1 degrees
Seth Lugo, 16.5 inches, 32.1 degrees
OK, one more list before we go. If we squeeze the data a bit tighter and look at pitchers with arm slots of 45 degrees and lower with a minimum of 50 four-seam fastballs thrown, something fun happens with Bubic — he generates elite four-seam ride for his arm slot, which is what makes his fastball so difficult to hit in the zone.
(You’ll also notice none of MLB’s overall leaders make this list. That’s because they all pitch from arm slots higher than 45 degrees, most of them closer to 50, making it easier to achieve those gaudy 20+ inches of vert.)
Connor Gillispie (MIA), 19.5 inches
Ryan Pepiot (TB), 19.3 inches
Shota Imanaga (CHC), 19.3 inches
Jason Adam (SD), 19.3 inches
Lake Bachar (MIA), 19 inches
Emilio Pagan (CIN), 19 inches
Bowden Francis (TOR), 19 inches
Sean Burke (CWS), 18.9 inches
Kris Bubic (KC), 18.7 inches
Jeff Hoffman (TOR), 18.6 inches
Miss this week’s Royal Scrolls? Check it out for a preview of this weekend’s series in Baltimore with Kris Bubic facing Tomoyuki Sugano and Michael Lorenzen rounding out the three-game set Sunday against Kyle Gibson.
Fascinating look at this. I’ll be watching Bubic in person tonight so very timely.
I just want to make sure I remember correctly that iVB measures how much higher a pitch is than would be expected. So you'd see Lugo's curveball as a negative number, right?