Investigating average release extension

Let’s talk about extension, and in particular, let’s talk about average release extension. What does that mean? Well, release extension is how far from the rubber a pitcher actually releases the baseball. The more extension you can get towards home plate, which means your pitches have to travel less distance, and thus the batter has less time to react. Simple concept, right?

There are lots of things that determine release extension. You might think that it’s mostly tied to a pitcher’s height and the length of his arms, but while it is indeed a factor, that’s not the only thing at play here. Consider someone like long-armed, 6’5” Justin Verlander, for example, whose average release extension for his recent career (2015-20, the years pitch tracking covers) is 5.9 feet, lower than MLB average (which is usually between 6.1 - 6.3). This is caused by his relatively short stride forward in his mechanics and it means, among other things, that his fastball “plays down” in terms of velocity. Someone on the other end of the spectrum would be Jacob deGrom, who gets 6.9 (nice) feet of extension, way above average and one foot further than JV. This is one of the reasons his four-seamer is as devastating as it is: he simply releases it closer to the batter. Randy Johnson would be another excellent historical example of this.

There’s a lot of fun stuff you can do with data like this, of course. You can check out the leaders for 2021 (some of the leaders include guys like Tyler Glasnow, Aroldis Chapman, Zack Wheeler, Kenley Jansen, Freddy Peralta... You get it), you can go for league average (6.3 in 2021, well higher than the 6.0 it was in 2019), and so on.

Major League Baseball

First and foremost, just to put the data out there, the Rockies as a staff had the second-lowest average release extension in all of baseball (6.1), with only the Houston Astros (6.0) behind them, but that’s not a terrible thing by itself. The Dodgers (6.2) are bottom five as well, so while this is not something that would make or break a team’s pitching staff, there is at least some degree of correlation between average extension and quality of pitching, especially on fastballs:

Baseball Savant

There you can see the average release extension of every team in 2021 (X axis) and the xwOBA allowed (Y axis), and keep in mind that the xwOBA against is only against fastballs (four-seamers, sinkers, cutters). You can see the Dodgers as the biggest outlier, and I’ve marked the dots that represent the more extreme teams as well. Let’s kick it up a notch:

Baseball Savant

The X axis still represents extension, but the Y axis now represents the gain or loss of perceived velocity, again on fastballs. You can see the connection is strong (don’t ask me what’s up with the Giants and Brewers, I couldn’t answer that as of now), and also that it basically mirrors the chart before it. You can also see the Rockies are a bit of an outlier themselves. I suspect that has to do with the very high average velo of the staff as a whole and Coors Field, but I can’t confirm that, so don’t take my word for it.

Anyway, the point of all this is that extension is important and very good for a pitcher, because velocity is very important; it leads to more swings and misses, a higher ability to get away with mistakes, and more. How do Rockies pitchers fare here?

The Rockies

Here is the data, made up of all pitchers to throw at least one pitch for the Colorado Rockies in 2021 (I took the liberty of excluding guys who likely won’t pitch for the team in 2022 from the chart below). Here they are based on average extension:

Two things stand out to me above all else. One, Gomber and Julián Fernández have terrific extension, and two, Germán’s is almost a foot shorter than average. This is probably another reason why his fastball doesn’t miss all that many bats despite its above average velo, because that short extension causes this:

Baseball Savant

(I know Yency won’t be a Rockie anymore, but I wanted to single him out anyway because he was the biggest outlier on this chart) You can see how strong the correlation between extension and perceived velocity is here, and you can see the loss of velocity (the data is here). In other words, while Germán’s average fastball last season was 94.8 MPH, hitters perceive it as roughly 93.8 MPH. Someone like Julián Fernández, on the contrary (watch out for that name next season if he can develop even 35/40 grade command), gains about 1.3 MPH in perceived velocity thanks to excellent extension, making his average 99.0 MPH heater look like 100+ on the regular. Not too shabby.

This is just the tip of the iceberg, of course. Extension, arm angles, pitch shapes, all the things that modern pitching development uses to turn pitching into plain and simple bat-missing, are only barely available to the public. Baseball Savant is a wonderful way to dive into the surface level stuff, but there’s a lot of things I don’t have answers for. Why does Gomber’s fastball not gain the perceived velo you would expect based on his extension? What in the world was going on with the Giants and Brewers in that other chart? Can extension be modified without messing with a pitcher’s mechanics too much? Are the Rockies taking this stuff into account when drafting, developing and acquiring pitchers? Who knows! But writing about topics that ultimately possess a tiny degree of relevance is one of my favorite things, so that’s what this whole thing was for. I encourage you to dig through the data if you’re a numbers nerd like me.

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A Visualized Primer on Vertical Approach Angle (VAA) | Fangraphs

This is nerd stuff, so it’s perfect for if you’re into that. VAA is, essentially, the angle at which a pitch approaches home plate. Tall pitchers with big, overhand deliveries (think Justin Verlander) have a steep VAA, and sidearmers (think Max Scherzer) have a flat VAA. Vertical Approach Angle plays a big part in generating swings and misses, which is basically all modern pitching development is about.

Sho-Time! MLB The Show 22 coming April 5 | MLB.com

I don’t recall a more obvious cover athlete than Shohei Ohtani for MLBTS 22, and I’d like to take a moment to brag about the fact that I called his MVP award when the Purple Row staff made season predictions on this very site.

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