Ever since pitch f/x arrived in baseball, the topic of pitch movement has become a pretty popular topic across baseball fans. People started to not only evaluate a pitcher with their eyes, but with numbers like Horizontal movement.
Early on, we’ve realized that the best fastballs weren’t necessarily the highest spinning ones. For example, Josh Hader’s fastball spun at a below-average 2,123RPM despite the success it’s had.
Because not all spin converts to the movement of the pitch.
What does “cutting the fastball” look like?
On a typical fastball, the fingers pull down behind the ball, creating the spin direction that is in-line with the trajectory of the pitch(the black line on the ball)
When the ball is cut, the fingers pull down to the side of the ball, creating the spin that runs across, diagonally compared to the trajectory of the pitch.
So what changes does it make?
In short, cutting the fastball can create 4 effects to the characteristics of the pitch:
- Reducing velocity
- Tilting the spin axis counterclockwise
- Increasing spin rate
- Reducing spin efficiency
In order for the arm speed to fully translate its energy to the ball, it has to apply the force directly behind it.
Think of it as shooting a soccer ball.
If you kick the side of the ball, not only will it not go straight, but it will be slow compared to the kick with solid contact.
Tilting the axis
When the axis tilts counterclockwise, the most notableeffect would be the horizontal movement. To elaborate, I’ll use an average fastball as an example:
- An average fastball has a spin axis of around 1:00, creating a 2:1 ratio of Vertical : Horizontal movement
- It has about 8 inches of “armside fade”(horizontal movement to the right) to it.
- An average cutter has a spin axis of around 11:30, creating a 5:1 ratio of Vertical : Horizontal movement
- It has about 2 inches of “gloveside cut”(horizontal movement to the left) to it.
- The combination of “armside fade” and “gloveside cut” creates a total of 10 inches of horizontal contrast between the two pitches.
- Our eyes, which are used to the fastball’s fade, perceive that as the cutter horizontally moving 10 inches.
Increasing Spin Rate
The more the ball is cut, the higher spin is generated. Brian Bannister has a solid explanation:https://majorseventh.blog/media/7b7837c683b76150c72f621eabec4c05
However, the extra spin that’s created seems to be sacrificed by the lower efficiency, explained below:
Reducing Spin Efficiency
As noted before, when the ball is cut, there’s more spin that runs diagonally compared to the trajectory.
We know that the “diagonal” spin is a combination of top/side spin and gyro spin. So, cutters/sliders typically have a lot lower spin efficiency than fastballs.
Hence, you can infer that the pitch with the lowest spin efficiency is the slider.
So what makes a good cutter(cut-fastball)?
Before we discuss this topic, I’d like to note that there are two types of cutters: The cut-fastball and the slutter/hard slider. The differences will be outlined later in the Pitch Classification Series.
For now, we will only talk about the cut-fastball, as it is the pitch that has been described in this article; simply speaking, a cut-fastball is a fastball variant, while a slutter is a slider variant.
It’s important to distinguish the two pitches, as the usage and the outcomes of these are very different.
There’s 3 components of a good cutter. Although I will describe what they are, I will not explain the exact mechanisms in which they work, as they require too much information to fit in this one article.
- Horizontal Movement
- Vertical Movement
Horizontal movement is the most important thing about the cutter; it’s why the pitch is called a “cut” fastball.
Having more horizontal movement has 2 benefits:
- It creates a bigger contrast with the fastball, such that the pitch moves away from the barrel(into the handle, or to the “cupping” of the bat). That reduces exit velocity.
- If the ball is pitched to the other side of the plate, then more break creates late break. This is another complicated topic that will be explained in a separate article.
Velocity is also very important when it comes to the cut-fastball.
Higher velocity also has 2 benefits:
- If it’s faster, it’s harder to hit(duh;;)
- The less velocity the pitch takes off from the fastball, the less time the hitter has to adjust to the cutter. That decreases the frequency of barrels.
This is the case where it isn’t necessarily the “more is better” scenario. In this case, the characteristics are similar to the fastball:
- The more rise it has, the more Swing&Miss it creates
- The more drop it has, the higher GroundBall% it creates, and less homeruns it allows
Two things are noteworthy about the vertical movement of the cut-fastball:
- The amount of movement is closely related to the spin efficiency of the pitch(the degree to the amount of “cut” on the ball)
- As said before, the more “cut” on the ball means that the finger pressure is more at the side of the ball, which means less velocity
When accounted for these factors, the vertical movement of the cutter seems to vary quite little.
On average, the cut-fastball is about 2–4mph slower, drops an extra 7 inches compared to the fastball.
Kenley Jansen and Mariano Rivera are the famous outliers. Both had a very high velocity(similar to the league average fastball) with quality horizontal movement(4–7 inches gloveside), while Jansen’s pitch dropped 4 inches less and Rivera’s pitch dropped 4 inches more than the average fastball.
In result, Jansen posted a career 13.3 K/9IP, while Rivera posted a career 0.5 HR/9IP.
On a side note, Tim Lincecum’s fastball started to cut in 2009, and quite literally became a cut-fastball since 2010, only increasing its cut as time went by. The movement progression surprisingly lines up quite well with the decline in his velocity, which leads to…
The Natural-Cut Syndrome
This is a phenomenon observed across multiple pitchers who faces decline in their fastball velocity. For these particular pitchers, the following things happen as they age:
- Fastballs decrease in velocity, while other pitches maintain the velocity or decrease slightly
- Gloveside horizontal movement on the fastball increases, while the vertical movement decreases
- Spin rate on the fastballs increases, while spin efficiency decreases
There is a theory for why this phenomenon occurs to some pitchers. I might outline them in the future.
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