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Pitching at Altitude, Part 2: Mile High Fastballs

Welcome to “Pitching at Altitude”, a six-part series where we’ll take a data-based approach to solving the near 30 year old dilemma that is pitching at mile high elevation.

Welcome to the second entry of my new data-based pitching series about the Colorado Rockies. After evaluating almost every pitcher on the roster during the extended “Crafting a Gameplan” series (which you can find here), this time we’re tackling a more widespread, fundamental topic: pitching at altitude. It’s no secret that this is difficult and a problem the Rockies themselves have grappled with for years.

Even now, after 30 years, there doesn’t seem to be an obvious answer to pitching at high elevation. What we’re going to attempt to do in this series is use data and physics to understand the dynamics that make throwing a baseball at mile high elevation radically and uniquely different from any other place.

As a reminder, this series will be divided into six parts:

  • Part 1: The General Effects of Elevation
  • Part 2: Mile High Fastballs
  • Part 3: Sinkers & Cutters
  • Part 4: Breaking Balls
  • Part 5: Changeups & Splitters
  • Part 6: The Perfect Rockies Pitcher

Today, it’s time to talk about the good ol’ heater. I hope you enjoy the series and find it informative.

In general, when one might think about what pitch type altitude hurts the most, the most typical answer will be the curveball. But what if I told you that’s actually not the case? Let’s go over four-seam fastballs at high elevation: how the mile-high environment affects them, what kind of fastballs translate best at Coors Field, and how to scout good fastballs in general.


Not just the most common fastball, but also the most common pitch in the major leagues, the four-seam fastball (4SF) is the first pitch everyone learns to grip and throw as a pitcher. Despite the sharp decrease in fastball usage across baseball over the past decade, it remains a fixture of the game.

Its role has changed as pitchers move away from the idea of “establishing the fastball”; it’s now treated mainly as just another offering in a pitcher’s repertoire, often used at the top of the zone to create swings and misses, pop-ups, and called strikes.

As we’ll see, not every four-seamer is the same, and depending on the profile we might think of different uses for it. First, however, we’re going to take a look at what variables contribute to making a good 4SF, then see how altitude impacts them and, in turn, how that could impact the Rockies’ evaluation of this pitch type.

What Makes a Good Four-Seamer?

As I said, there are many quirks to a four-seam fastball that contribute to creating a wide variety of profiles. For example, some 4SF have a lot of run to the armside of the pitcher, which can be because of arm slot, where a pitcher applies force to the ball, etc. Others have the opposite movement, instead featuring noticeable gloveside cut.

For simple scouting purposes, however, horizontal movement is a secondary factor that plays a bigger role in determining fastball usage than fastball quality. Instead, the three main factors you’ll look usually at when evaluating the quality of a four-seamer are the following:


The first one is very straightforward: How hard is this fastball? As pitching has become more of a max-effort activity, bullpens have increased in size, and training has gotten better and better, the average fastball velo in the big leagues has skyrocketed since the start of the century.

In 2002, the average MLB 4SF was slightly below 89 MPH. In 2022, it was close to 94 MPH, with righties throwing a bit harder than lefties, as per usual. With everyone throwing hard, the velocity requirements keep increasing. Anything at 91-92 MPH or below can be an obstacle in a pitcher’s quest to get outs.

Even 93-94 is just not what it used to be. It’s only once you get past the 95 MPH threshold that you start seeing significant gains, with every tick above that being a significant boost to predicted success. It’s also important to consider effective velocity; pitchers with great extension down the mound (Gavin Hollowell) release the ball closer to the batter, making velo play up. On the opposite side of the spectrum, short striders (Germán Márquez) can have their velo play down.

The main thing velocity buys a pitcher is margin for error within the strike zone. It is so much easier to get away with 98 down the middle than 94 down the middle. So what’s plus velo? Nowadays, averaging 96+ on the fastball is probably what I would describe as plus velocity, so there’s a good place to start. For a starter, 95+ also applies.


The term “rising fastball” has been a household name in the game for generations, referring to a fastball that seems to have a certain kind of late life that just doesn’t move in expected ways.

Many of the great pitchers had this, of course: Clemens, Roberts, Seaver, Randy Johnson, Dwight Gooden at his best, Koufax, Verlander, and so on. That phenomenon happens courtesy of IVB. IVB is, in essence, how many inches of vertical movement a pitcher creates on his four-seam fastball thanks to the way he backspins it through the Magnus Effect we went over in the first entry. Again, here’s JV:

Efficient backspin allows the baseball to fight gravity and drop a lot less than expected, resulting in swings underneath the ball. This is a natural pairing with throwing the ball up in the zone, of course, and it’s the main variable many teams chase after today.

A quick disclaimer: IVB numbers are presented without gravity, and they are not the same as “drop,” which is what you might see on a website such as Baseball Savant. IVB is simply the raw, in-a-vacuum break created by the Magnus Effect.

For reference, across MLB, the average IVB on a 4SF tends to be around the 15-16 inch mark. 18 inches of IVB is good, and anything nearing or surpassing 20 is elite. This is that “hop” and “carry” that scouts have talked about for years, now measured accurately. If you’re interested, you can check out IVB numbers on the “Specs” section of this public leaderboard from Alex Chamberlain.


After velocity and vertical movement, the final variable we’re going to look at is Vertical Approach Angle, which you can also check out in Alex Chamberlain’s public leaderboard.

The easiest way to think about VAA is that it refers to the angle at which a pitch crosses home plate, and for four-seamers we want this angle to be as flat as possible to induce whiffs and soft airborne contact. Anything at -4.5º of VAA or better (closer to the zero value) is what I’d call plus. What are some of the main factors that affect VAA?

  • Location. This first one is obvious - a pitch thrown up in the zone enters the zone at a flatter angle than a pitch thrown down in the zone, hence why power pitchers tend to live in the upper third of the zone instead of pounding fastballs at the knees.
  • Release height. This will immediately make sense to you if you picture the pitch’s trajectory from a side view. The higher the release, the more downhill its path towards home plate, but the lower the release, the flatter its path.
  • Release extension. A very simple premise here: The closer you release the ball to home plate, the less time the baseball has to drop due to gravity, and the better it’s going to play. Not to mention, of course, that velocity plays up in those cases as well.
  • Pitch shape. Finally, the pitch’s actual movement also plays a role in VAA. You can throw upstairs from a sidearm slot and with elite extension towards the plate, but if the pitch you’re throwing is a sinker, that baseball is going to be heading downwards as it gets to the plate, and the VAA is going to be steeper than it could be.

And there you have it — velocity, vertical movement and VAA is what you’re looking at when evaluating a four-seam fastball on a basic level. Fastballs that are plus in all three categories are sometimes called “triple-threat fastballs” and are easy to project as dominant offerings. But it’s possible for a fastball to “only” be plus in two of the three categories and be dominant.

Look at Astros pitcher Cristian Javier (the 2022 version) for an example: His fastball had average velo (93-94 MPH last year), but because Javier was so good at creating vertical break on it (19ish inches of IVB), threw upstairs consistently, and has a release point that is lower than usual, its VAA (-4.0º) is also plus. Two of the three qualities are there, and his fastball is an excellent pitch.

Mets closer Edwin Díaz is another example. In his case, Díaz’s plus-plus velo (99.1 MPH) and elite VAA (-3.7 VAA, thanks to his combination of low release point and elite extension) work together to overcome his measly 13.5 inches of IVB, which is quite poor, and make his fastball dynamite anyway.

After these examples, and now that we know what a plus four-seamer looks like, here’s the money question: What happens to this pitch type at altitude? Let’s take a look.

How Does Altitude Affect Four-Seamers?

We’re going to tackle this in a few way, and don’t worry: We’ll get to basic results in a while. First we need to understand how the environment will affect a 4SF, and for that, we’ll go back to some of the concepts explained in the first entry, in particular the Magnus Effect.

As we know, air density is lower at high elevation, and this has a direct effect on how pitches move. We also know that the Magnus Effect is the main force that enables a 4SF to fight off gravity thanks to effective backspin, and that because of that lower air density: The baseball has less air to work with as it spins towards home plate.

Therefore, we can draw some immediate and accurate conclusions:


This is the biggest change. Because the baseball has less air to interact with, the Magnus Effect is noticeably reduced. As such, it is estimated that a four-seam will, on average, lose around 3-4 inches of IVB at Coors Field when compared to sea level.

Remember the scale of IVB we talked about earlier, where 15-16 IVB was average and 19 was excellent? Well, a 19 IVB fastball will come to Coors Field and end up right in the 15-16 range, offering basically mediocre carry. Altitude will take a four-seamer with plus vertical movement and make it average.


Like vertical movement, armside run on a fastball is also often a part of the Magnus Effect, frequently created by pitchers with lower slots and/or a mechanical bias towards pronation (applying force on the inside of the ball) by introducing some level of side spin on that baseball. At Coors, you can expect that kind of run to also be cut by around three inches on average.

You can see an example of that in this Sandy Alcántara start from 2021, where his four-seam lost an average of three inches of run (and three inches of carry) compared to his season averages. Alcántara is a pitcher whose four-seamer is an outlier in terms of run, but he lost it at Coors and got lit up in his worst start of 2021.


On the other hand, and based on some of my own research through Baseball Savant, 4SF with some level of glove-side cut tend to keep most of that cut even while losing their carry, at least to a certain degree.

In my experience, this applies to both super high spin fastballs (someone like the Dodgers’ Julio Urías) and lower spin versions (like Antonio Senzatela). Since it’s a stable feature, it makes sense to me to favor it... but we’ll cross that bridge when we need to.


There is one positive to the lower air density, however, that being that perceived velocity is actually higher at Coors Field than it is at sea level. This is, of course, because there is less air to offer resistance to the baseball as it travels towards home plate.

Here’s something interesting: Coors Field is the only regular ballpark in MLB that, since 2015, has seen its perceived velocity be higher than the actual out-of-hand velocity, and it’s not even close. Four-seam fastballs at Coors have had a perceived velo 0.3 MPH higher than the actual velo — every other ballpark has seen at least a 0.1 MPH drop. This is something to keep in mind.

The Basic Results

With all of that fresh, let’s see some basic results and we’ll be able to make sense of them. The chart below considers all four-seam fastballs thrown across MLB from 2015-2022:

Four-Seam Fastballs (2015-22)

Venue Run Value (per 100) wOBA xwOBA Exit Velo (MPH) Launch Angle (º) Whiff% Chase% Velo (MPH) Per. Velo (MPH)
Venue Run Value (per 100) wOBA xwOBA Exit Velo (MPH) Launch Angle (º) Whiff% Chase% Velo (MPH) Per. Velo (MPH)
NOT COORS 0,06 ,346 ,348 89,8 17,9 20,6% 23,8% 93,4 93,1
COORS 1,09 ,392 ,362 89,4 9,9 17,3% 21,8% 93,6 93,9
Difference 1,03 0,046 0,014 -0,4 -8,0 -3,3% -2,0% 0,2 0,8

(Run Value is the run impact of an event based on the runners on base, outs, ball and strike count. The higher, the more runs it will produce. wOBA stands for weighed on-base average; basically, OBP that takes the manner you reached base into account. xwOBA is expected wOBA, which takes walks, strikeouts and contact quality into account.)

Some things probably surprised you, but here’s what I took from it:

  • Because of their lack of movement, 4SF at Coors create less whiffs and better swing decisions. A drop of a couple of percentage points might not seem like much, but it’s really big in practice. It means that you need to be extremely precise with your location to succeed.
  • 4SF at Coors are actually hit on the ground more often. I suspect that some of this is the Rockies’ insistence of throwing heaters down in the zone, but it makes sense that batters used to heaters carrying a bit more at sea level might hit them at lower launch angles on average when they come to Denver.
  • As expected, perceived velo goes way up. That is almost a full tick harder than other ballparks on average. This is something to weaponize by going all in on velocity, but we’re about to talk about that in more detail later.
  • 4SF at Coors create very poor value. It’s a bit of a spoiler for when I use the full chart with every pitch type in the final entry, but four-seamers are tied for the highest increase in Run Value and tied for the second-highest increase in wOBA out of any of the pitch types we’ll be going over in this series. They suffer more at altitude than just about any other pitch type.

Scouting Altitude-Proof Four-Seam Fastballs

So, with all that information laid out on the table, here’s where I’m going to give my personal assessment on how I’d look for four-seam fastballs if I were a part of the Rockies organization. The goal would be to find and develop fastballs that are not only good in a vacuum, but also hopefully have a smooth a transition to altitude.

Considering that the variable of four-seamer quality that suffers the most by far is IVB, it makes sense to put the main focus instead on the other two: velocity and VAA.

  1. Velocity is king. Since we can’t rely just on vertical movement, a good 4SF for a Rockies pitcher must be thrown hard. At sea level, you can get away with 91-93 if the outlier IVB is there, and sometimes thrive. At altitude? Not so much. Our ideal four-seamer needs to be hard.
  2. Favor pitchers with plus extension down the mound. Elite extension not only helps velo play up, it is also closely related to flatter VAAs by virtue of releasing the ball closer to the plate and frequently leading to lower release points as well.
  3. Four-seamers go up in the zone. You can have velo and extension, but if you’re throwing at the knees VAA goes out the window and you’re going to get hit hard. If we want to throw something hard at the knees, sinkers are the pitch for that, not four-seamers.
  4. If we have to choose between run or cut, we favor the latter. This is simple; Run suffers, cut really doesn’t, so the stable variable is the one that makes more sense to keep. This would also give us tools against the opposite hand. We’ll go over that in depth in later entries, but here’s the basic notion: Fastballs with cut tend to have more neutral platoon splits, while fastballs with run tend to perform better against the same hand. So if your fastball cuts and you’re a RHP, it makes sense to prioritize it against LHH and use a sinker instead against RHH.
  5. Favor pitchers with lower release points than usual. The final piece of the puzzle is release point height, which directly helps VAA be flatter and gives us margin for error within the zone. Low release points is why I believe Ryan Feltner’s 4SF can have utility despite unimpressive shape, and why I’m desperately begging someone to convince Justin Lawrence to throw a four-seamer. Here’s a chart to convince you a bit further:

Four-Seam Fastballs at Coors Field (2015-22)

Release Point Height (ft.) Run Value (per 100) wOBA xwOBA Exit Velo (MPH) Launch Angle (º) Whiff% Chase% Total Pitches Pitch Velo (MPH)
Release Point Height (ft.) Run Value (per 100) wOBA xwOBA Exit Velo (MPH) Launch Angle (º) Whiff% Chase% Total Pitches Pitch Velo (MPH)
<= 5.5 0,80 ,386 ,358 89,0 11,8 19,6% 23,0% 8233 93,7
5.5 - 6 1,08 ,388 ,361 89,5 9,6 17,5% 21,9% 34828 93,8
>= 6 1,15 ,396 ,362 89,3 9,8 16,5% 21,2% 29794 93,4

The difference in whiff and chase rates is noticeable, and it makes me believe I’m totally right in suggesting that favoring low release points is a good idea.

Obviously, this is not to say that IVB is completely useless — the Rockies play 81 games on the road, and even if Coors cuts IVB by a few inches, 19 IVB that turns into 16 IVB is much better than 16 IVB that turns into 13 IVB. It’s just that IVB can’t be the only plus factor that sets a Rockies four-seamer apart.

An example of a Rockies pitcher with a great 4SF is newcomer Nick Mears. Over the past two seasons, Mears’ heater has averaged 95.7 MPH, 19 inches of IVB and a -4.4º VAA, all ranging from above average to plus.

Mears gets fantastic extension down the mound and his movement has been creeping up lately, all of which makes his heater play up even more. It’s not perfect for altitude (his release point height is virtually league average), but it’s still a great heater and foundational piece to Mears’ arsenal.

A Rockies pitcher with a subpar 4SF that doesn’t translate well to altitude would be Austin Gomber. Gomber has well below average velo (91.3 MPH from ‘21-’22, and creeping lower than that in ‘23) and by virtue of his extremely high release point, his VAA is a really steep -5.9º. Both of those variables are poor.

The lone area where Gomber shines is IVB, where he routinely gets to 19+ IVB on the road thanks to his ability to impart efficient backspin on the baseball. It’s enough to make his heater play okay-ish on the road. At Coors, however, that variable becomes average and pairs with the poor velo and VAA to create a bad fastball.

Final Thoughts

If you thought that the pitch most impacted by altitude was a breaking ball, I hope this piece has made you reconsider. Four-seam fastballs are heavily affected by the effects of altitude and its environment, as the reduced Magnus Effect strips an important part of a heater’s movement from it and makes it flatter. This leads to less swings and misses and better swing decisions, making the margin for error extremely small.

We all know that the Rockies throw too many fastballs in general. We also know that they don’t really use the top of the zone as much as most teams do, but I would argue that in the current staff, there is such a blatant lack of good 4SF that this wouldn’t be the huge difference-maker to make the pitching staff perform far better.

The Rockies only have two four-seamers with truly plus carry, those of Mears and Gomber. Nick Mears’ heater is legitimately great, but Gomber’s is severely limited by some of the other factors we explained. That dominant kind of fastball shape is something that is virtually non-existent in the current 40-man roster.

The rest of the MLB staff? Not many good heaters. There are some solid four-seamers (Ryan Feltner, Germán Márquez when he throws hard, Gavin Hollowell’s fastball has good utility thanks to VAA and his excellent extension), but aside from Mears and maybe Hollowell, all are more situational offerings than anything dominant.

There are two fast-rising relief prospects in the system with excellent four-seamers, however, so brighter days might be ahead. Lefty Evan Justice and righty Victor Vodnik are two relievers with low release points, excellent velo and adequate shape. Justice features deception and outlier lefty velo, while Vodnik has plus-plus velocity and good action. Both are primed to be late-inning arms, and their heaters will be crucial for that.

If the Rockies are going to start developing good four-seamers, they need to not only embrace throwing them upstairs and throwing fewer heaters in general, but they also need to overhaul how they think about fastball shape and approach angles, and not be scared of the flyballs generated by pitching up in the zone. The rewards of being able to beat hitters upstairs (using the entire zone, being less predictable, having more weapons in two-strike counts) far outweigh the downside, even at Coors Field.

Another thing: If a guy naturally cuts his four-seamer (a.k.a. young Germán Márquez), don’t teach it out of him. It will give him an identity, a weapon for opposite-handed hitters, and an easier transition to altitude that will be lost if that is changed.

And there’s more: Just because a guy throws hard and has solid command doesn’t mean he has to throw a lot of fastballs. At Coors, one should often substitute the word “fastball” with “the worst pitch I have, and deploy it accordingly.

Baseball has changed, and the ideas of “fastball count” or “establish the fastball” are all but gone. Pitching in the harshest environment in baseball for 4SF (and fastballs in general) means that taking aggressive measures in order to survive is a must: if you don’t adapt, altitude will eat you alive.

Therefore, in my opinion, four-seam fastballs should be looked at as complementary pitches through a Rockies lens: weapons to use to change eye level and beat hitters upstairs, opening up the zone for everything else we’ll throw far more often.

The Rockies should lean heavily into velocity and VAA, favoring pitchers with low release points and plus extension, and favoring cut over run as far as secondary movement characteristics go. Some of this has seemingly already started to happen (see: Sullivan, Sean).

Of course, this doesn’t mean that every single pitcher has to follow this mold: Justin Verlander’s fastball may be a poor fit for altitude in a vacuum, but if there’s a level of outlier talent present, that should be the main priority. If, in an alternate universe, the Rockies had a shot to get prime Verlander, they should’ve been all over it.

Adapting to your environment, using data, embracing an aggressive and proactive style of pitching, and keeping an eye open for outlier skill: that is how you develop quality four-seamers that can survive and thrive at Coors Field. The fastball is not the all-important pitch it used to be, but that doesn’t mean it can’t be a great weapon.

So, that was the four-seam fastball. It was a long explanation, I know. Funny behind-the-scenes fact: originally, Pt. 2 was meant to go over all kinds of fastballs - 4SF, sinkers and cutters. However, the explanation took me longer than I thought it would, so we split things up in order to keep the length of this piece under, say, 6000 words. Next up: sinkers and cutters. See you tomorrow!

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