Analyzing One of the Most Dominant Pitches in the Game: Justin Verlander’s Slider

Every pitcher hopes to be able to command each of their pitches. However, most of the time it is almost impossible to know exactly how a pitch will move each time. Below is a zone chart that I will be referencing throughout this piece to help describe pitch location.

Justin Verlander’s Slider is dominant. It could be better though. He averages 4.2 inches of horizontal break against right-handed hitters. On the other side, he averages 3.9 inches of horizontal break versus left-handed hitters. If you are asking, “Does .3 inches really make a difference?”, the answer is yes, yes it does.

In no way am I knocking Verlander’s Slider because posting a 35% whiff rate against left-handed hitters is insane. But why not make it better? The .3 inches of horizontal break is a difference between the ball crossing the middle of the plate or jamming an opponent. Against a right-handed hitter, the ball more often than not ends up in zone 3, 12 or 14, however, against left-handed hitters, while the ball also frequently lands in zone 14, a ball ending in zone 6, 9 or 12 is more dangerous.

Verlander’s Slider is most effective when it reaches that bottom zone (14), which is justified by his high whiff % in that zone. However, left-handed batters see a higher percent of pitches over the plate and up than right-handed batters do. Then, this allows lefties to have a more optimal launch angle.

The next heat map will illustrate my point that even though Verlander is getting a good amount of horizontal break on his Sliders against left-handed opponents, it is not enough.

It makes sense that left-handed hitters would have an easier time with that location just because the location that the ball ends up in is easier to hit. There is no point in just accepting the fact that his Slider is less effective against left-handed hitters especially since he uses this pitch 28.7% of the time.

With almost all of Verlander’s pitch metrics being completely the same no matter the hitter’s handedness, this was a tough problem to tackle.

I noticed however, when Verlander throws a Slider against a right-handed batter, his release side averages -1.72 feet. Then, when he throws a Slider against a left-handed batter, his release side is averages -1.75 feet. This difference is not due to where he stands on the rubber. I watched several videos of him facing both batter types and Verlander is consistently standing right in the middle of the rubber. I understand that this difference is extremely small, but I ran a t-test to see if the difference in mean was statistically significant, and it was.

In this visual, you can see the means do not overlap and there is very small overlap altogether, so I can conclude there is a difference between his release points when throwing to righty and lefty hitters. So now that I found the difference, I wanted to see the effect it had on his Slider movement. In short, release side is correlated with plate location. Release side can affect where the ball ends up when it reaches the batter. Due to his release side being more negative against left-handed batters, the ball actually ends up more often over the middle of the plate.

If Verlander’s Slider does not cut enough down and ends up higher than usual against righties, that ends up being just fine because they still on average struggle against that location. However, if that Slider does not reach zone 14 against lefties, the heat map of hitter launch angles proves it could be hit hard.

I realize that such a small difference in release points is difficult to change, but I believe I found a way to reduce the risk against leaving the ball over the plate for lefties. Verlander’s Slider velocity is negatively correlated with horizontal movement. While correlation between two variables does not mean they have an effect on one another, I believe there is evidence that points to a cause and effect relationship.

Out of all the zones against left-handed hitters, Verlander most often throws in zones 5, 6, 9, and 14. There is no clear relationship between release speed and horizontal movement, which leads me to the point that there are numerous factors causing a change in his slider movement.

Even though the relationship between release speed and horizontal movement is not strong or direct, there are still underlying characteristics that should be considered. First of all, spin rate has a known effect on release speed and sliders obviously generate a lot of spin. Next, by an increase in spin rate, I believe this will give Verlander better command over his pitch.

Velocity is not really something that tips, especially if he just drops 1-2 MPH. He already has the same mean extension for Sliders against either batter handedness. I believe that focusing on velocity can allow for the biggest change in the effectiveness of the Slider against lefties. Lastly, reducing his velocity on the Slider will decrease the end height location of the ball making it more difficult to hit.

As mentioned before, Verlander averages 3.9in of horizontal break versus left-handed hitters. When his velocity drops on his Slider, as theorized earlier, the horizontal break increases.

To get to the coveted Zone 14, Verlander needs to have around .36 ft. of horizontal break. The reason he is so successful against right-handed hitters is because that is about what he averages when opponents stand on that side of the plate. However, because of the difference in release side, his average for left-handed opponents is slightly smaller. This explains why his Slider ends up more over the plate when facing a left-handed opponent.

Currently, he averages 87.5 MPH on his Slider no matter the batter’s handedness. By dropping just 1 MPH, Verlander can surpass the average threshold for a Zone 14 Slider and get the ball placed there with ease.

Here are all the averages of Verlander’s entire arsenal from the 2019 season. Having uniqueness amongst your pitch arsenal is very important. What makes a pitch useful is if its different from everything else you throw. So, if someone threw what they thought was 4 different pitches, but they all acted as a 4-Seam FB, hitters will have a much easier time against said pitcher. However, with Verlander all 4 of his pitches act differently making his arsenal that much more effective. My proposal to drop his Slider velocity down .5-1 MPH in order to compensate for the loss of horizontal movement would not jeopardize this phenomenon. Currently Verlander is sitting at an average 29.8 Bauer Units for his Slider. After running a simple linear regression, all else equal, lowering his velocity 1 MPH will only drop his spin rate down 10-20 RPM. So, worst case scenario, instead of averaging 87.33 MPH against left-handed hitters, he averages 86.33 MPH. His Bauer Unit would stay the same, and he would gain extra horizontal movement. Spin Rate does not seem to have a significant effect on his Slider’s horizontal movement, surprisingly. The decrease in velocity would cause a greater positive effect on his horizontal movement, than the negative effect a decrease in spin rate would cause on his horizontal movement.

Do not mind the size of the numbers, this linear regression would not be good at predicting the exact horizontal movement. However, this model does indicate that release speed has a greater effect on horizontal movement than spin rate does. Therefore, this can confirm my theory that slightly decreasing velocity on Verlander’s Slider can have a profound effect on the location of the ball when it crosses the plate.

Overall, this type of experiment would call for some trial and error. Attempting to throw a Slider had a slightly reduced speed could end up allowing the ball to end up more in on left-handed hitters. In the end however, I mentioned before that his Slider is one of the premier pitches currently in the big leagues. So why fix something that is not broke especially when he just won his 2^nd AL Cy Young award at age 36?

There was one piece of information I did not mention before. The Slider is not Verlander’s only breaking ball.  Against left-handed hitters, Verlander’s Curveball actually has a much higher Whiff % when he reaches zone 14.

I am not suggesting that he throws exclusively Curveballs to left-handed hitters opposed to Sliders because the opponents would know exactly what was coming. However, I am suggesting that given a certain situation, he would do more damage with his Curve. Verlander posted a 70% whiff rate in Zone 14, but also around 32 % whiff rate in the next top 3 most popular zone locations for his Curveball. Those are ALL higher than his whiff rates when comparing them to his respective top 4 most popular zone locations for his Slider versus left-handed hitters. Additionally, on average in the same 4 zones, Verlander’s Curveball averages a lower launch angle on balls that opponents even made contact on.

This whole piece was analyzing one of the most dominant pitches in the game today. What I was suggesting in regard to decreasing velocity to increase horizontal movement on the Slider, honestly might not work. There is data to back up my assertion as listed above, but again why fix something that is not broken? There is clear evidence however, that when a left-handed batter is up, Verlander has at least 4 out of 13 zones (that he already pitches most often to) that will cause the most trouble for opponents. I did not even talk about Verlander’s Changeup or 4-Seam, but by being able to interchange his two breaking balls throughout a game Verlander can strike anyone out no matter what side of the plate they are standing.