The extreme angles of the Astros rotation

Alessandro Zilio
7 min readMar 6, 2021


Let’s start with some good news: baseball is back!

Spring training is underway, which is a great opportunity to get reaccustomed to balls hit into outer space and nasty pitches worthy of Pitching Ninja recognition.

There’s also the classic heavy dose of unpredictability surrounding this magical pastime: on the positive side some Guys You Forgot and rookies coming out of the blue could break your team’s 40 man roster and be a revelation, a la Daniel Bard; on the negatives hold your breath, sit tight and hope no one in your rotation gets a trip to Dr. Andrews.

On a lighter note, you’ll have to bear some weird sights: Arenado manning third on a Cardinals uniform, Springer (miss ya babe) leading off for the Blue Jays and the absence of a Japanese pitcher in the Yankees rotation.

Still, the bad news are far from vanished in the wind: we are, as we were last season all along, in the middle of a pandemic, which means few or no fans in the stands, masks not only for catchers and umpires, the restlessness that comes with tests, results, contact tracing and, frankly, the mere existence of a plague that took away too many, legends of this sport and people like us as well.

For the sake of morale, nostalgia, and this post for that matters, allow me to take you back to 2016: those were the days, eh!?

Close your eyes and remember. You could still greet your friends with a warm hug and some fancy handshakes, maybe go to a game and witness the elation of a walkoff bomb along with tens of thousands of fans.

The world still sucked, but a little less: Cubs fans celebrated the end of a curse that only Bela Guttmann could match, Fernando Tatis jr was just the son of the sole player able to hit two grand slams in an inning (sorry Chan Ho Park), Game of Thrones was the bee’s knees and BTS were just a boy band raking in South Korea.

Baseball had only just began to greet the revolution called Statcast, and with all the new data and some poetic license a new term was (wrongly) coined: the Launch Angle Revolution.

While hitting the ball hard has always been a well-known and preached concept, the existence of a measure encapsulating the loft in a swing was a breakthrough that led many hitters to change their approach in a mission to send more (juiced) balls in the air and out of the park.

Obviously, for a Justin Turner or JD Martinez, guys who made quite the turnaround by creating more conductive and air-oriented swing paths, there are thousands of Eric Hosmers, still sending rockets down to the ground as in a war scenario, and Nomar Mazaras, always needy of some LA degrees to finally fulfill their promises.

What I want to talk you about is launch angle indeed, but for those who have to deal with it: pitchers.

As you, worldwide baseball fan, already know, launch angle and result is not a perfectly proportional link: hitting the ball with low LA returns a challenge to infielders and that is not a good idea if you are looking for some extra bases, yet put too much LA in the formula and things get even worse, in the form of lazy popouts and a pitcher’s best friend, the infield flyout.

Woah, too many words! Bask in the beauty of a graph, straight from Ben Clemens’ article on sweet spot:

from Clemens, FanGraphs, 2020

Now, this is 2019 batted ball data yet the result stands today as well: a productive launch angle, wOBA-wise, has to be between 0 and 35 degrees, while everything launched in the negatives or in the 40+ zone is wasted.

I know what you’re thinking about: we are missing a thing here! Exit Velocity it is, and it’s not a small component in the game we all love, so here’s Ben again pulling the weight:

From Clemens, FanGraphs, 2020

No big secret to be revealed here: hitting the ball hard, in the Statcast term of HardHit as we learned to appreciate, means getting better results whatever the launch angle imparted on the ball with a big time difference in the 25–35 LA range. Yep, those are the Barrels per definition, with the resounding wOBA that accompanies them.

What about those balls hit under the Barrel speed limit? Is the pattern the same? Ben, the floor is yours:

From Clemens, FanGraphs, 2020

Not really and here’s something I’ll go back to in my future endeavours on launch angle on a pitcher’s perspective: sometimes a SoftHit is worse than a HardHit, particularly when balls hit hard go on the ground to a good infield defense while teardrops fall into no-man’s land and not on the fire.

So what does it all mean for the guy on the bump? First of all you’d rather want someone who refuses the hard contact: bloop singles are a thing of beauty but they are hard to come by and not that hurtful, while a laser show is bound to bring the pain. There’s so much value in a Ryan Yarbrough when he’s adequately helped by his peers behind him.

Second, you’d rather have a pitcher whose offerings go back, when they do, at an extreme launch angle: anything negative and you got some activity for your infielders, anything over 40 degrees and your only enemy is the sun or some miscommunication (Eric Hosmer at it again…):

This is 100% wishful thinking: how many pitchers average negative or 40+ degree LA on batted balls against them? For the latter none, zero, zilch, nada but for the former? Here is where my journey started.

As I’m sure many of you do when you’re bored, I tend to roam around FanGraphs’ leaderboards and Savant player pages looking for a weird stat or trait that could make Average Joe the next big thing.

Given my love for pitching I was messing around with 2020 starter data, with at least 40 innings pitched to find some “solid” answers, and with launch angle when a great name came up sorting the list of pitchers from lowest to highest avg LA allowed: sadly-now-injured Framber Valdez.

As an Astros fan I fully appreciated the solidity of a supposed number 4 starter that ended up providing a lot of quality innings for a rotation depleted of now-Yankee Gerrit Cole and already-injured Justin Verlander, yet I wasn’t ready to what the leaderboard told me: he allowed an average launch angle on balls in play, considering only in innings as SP (64.1), of -1.0 degrees.

Did anyone manage to do better in 2020? Nope. Is anyone on his universe of low launch angles in the Statcast era (2015 on)? Yes, but just other three guys in all of five years: guess them!

No, just kidding, here they are: atop of the mountain stands once Astros ace…. Jarred Cosart! In an almost 60 inning 2016 he allowed an avgLA of -2.6 degrees, making it rolling more than the Brave Girls in this strange 2021. Next up the 2015 edition of professional worm-killer and oft-injured Brett Anderson (-2.1)and then who you thought at first, 2017 Astros legend Dallas Keuchel (-0.6). No other starter with at least 40 innings in any season from 2015 to 2020 achieved a negative average launch angle.

Does it stop here? No, because flip-flopping the same list returns another household name for Astros fans: Cristian Javier.

One of the young guys that weren’t supposed to contribute to the Houston cause yet called upon due to a barrage of injuries, Javier managed to look at Valdez and do the opposite: in 2020 he gave up an avgLA of 24.7 degrees, a bevy of flyballs.

Is anyone on his tail in Statcast history? Just a couple of guys: a 2017 rendition of AJ Griffin and his slow curveballs (24.6) and the master of infield flies himself, 2018 Marco Estrada (24.8).

No other rotation has ever had such a gap in conceded avgLA between two of his stalwarts as far as Statcast data tells me, but how big is the rift separating a groundballer as Valdez and a “fly to the sky” proponent as Javier?

Some pedantic technicalities: I’ve used the gghalves package to design these so called half violin plots, adding the red line at the 13 degree mark, the average LA allowed by “qualified” starters in 2020. The names you see are the top 5 in highest to lowest average LA allowed (plus a Lance McCullers Jr just because).

The difference between Valdez and Javier is stark: the former lives on the left of the red line, the latter on the far right, two brothers in arms divided by a wall as in mid 80s Berlin.

What makes it all so interesting is that not only they were on the same team, but both provided good value: Valdez leaded the way with 1.8 WAR while Javier only brought 0.3 to the table due to bad peripherals which stem from an abysmal BABIP (.185, 2nd lowest in 2020) although he has an history for such results in the minors due to his flyball tendencies so I’d take the over on his projections.

In my future posts I’ll examine both Valdez and Javier’s 2020 balls in play in more detail, looking for ways to group them and compare their allowed results. Prepare yourself for some clustering and messy graphs.

Until then, enjoy some Spring Training action. In the world we live in it may not be much, yet nothing sooths my soul as baseball, and peace is exactly what we all need the most right now.



Alessandro Zilio

Italian baseball stathead. I’ll write about MLB, NPB and Korean dramas. A lot of Astros related content and obscure references.