A Look at Extension and Movement
What is the relationship between extension, spin rate, and movement on breaking balls?
In the previous post, I showed that breaking balls usually have a lesser amount of extension than fastballs do. It seems that this is more of a result of the way pitchers throw these two types of pitches and doesn’t really have anything to do with velocity (because changeups and fastballs have similar average extensions).
On a fastball, the closer a pitcher is to the batter, the less distance the ball has to travel, the quicker the batter must decide to swing, and the faster the pitch is perceived to be. Therefore, having a lot of extension is ideal for fastballs. But we found in the last post that pitchers don’t seem to be getting this same extension on their breaking balls by about 4 to 6 inches on average.
Let’s look at Corey Kluber’s curveball as a case study! (A unique hybrid between a curveball and a slider, Baseball Savant classifies it as a curveball.) The previously linked FanGraphs article shows Kluber’s curveball grip. As we can see, it’s similar to a traditional two-seam fastball. But in 2018, Kluber has released his two-seamer more than 6 inches closer to home than his curveball. Surely, with grip held constant, Kluber could release his curveball closer to home if he wanted to. But he doesn’t.
This is further evidence that the optimal extension for breaking balls isn’t the same as the optimal extension for fastballs! But where is that optimal spot, and what does spin have to do with it?
Well I’ll be honest. I thought I was onto something here. But it turns out i’m not. I anticipated that curveballs with a high extensions would have a poor spin rate and/or less movement. Similarly, I thought curveballs with low extensions would be the same. In my mind, there would be a middle ground with a mid-level extension where curveballs have optimal spin rates and maximum movement. Here are the scatterplots:
If you look closely, we can learned a very important lesson here: look at the data before writing half of the story!
It’s certainly possible that each pitcher has his own optimal extension for his respective curveball. But even then, it wouldn’t be the same as his optimal fastball extension. So here’s what I would do if I was a little more technically skilled, and I’ll come revisit this topic after learning some more R:
Get all of the curveballs thrown in 2018. Find the z-score of each curveball’s extension in relation to its pitcher’s average curveball. Then, on separate scatterplots, I’d plot each curveball’s extension z-score on the x-axis with its spin rate, vertical movement, and horizontal movement z-scores (again relative only to the specific pitcher) on the respective y-axes.
But in the meantime, I’ll do this just for Kluber’s curveballs this season. Maybe this will provide any insight at all and salvage this post. Also, I’d prefer not to have made a gif in vein.
So here we go.
Nothing to see here.
Keep scrollin pal.
…
Ok. I’m going to accept defeat at this point. Until I cook up some better methodology, it looks like Corey Kluber’s extension on his curveballs is unrelated to their velocity, spin rate, and movement. Maybe extension just isn’t that important! And that’s ok.
Thanks for reading. For your troubles, here is that gif accompanied by a blurry freeze frame of Kluber’s curveball at release with his hand looking like a velociraptor talon.
