Article: Baseball’s Gatekept Pitching Metric: Inside Vertical Approach Angle

[Maddie Landis]

Teams are drafting under-the-radar pitchers who evolve into aces at the major league level. Many of baseball’s current aces were selected in later rounds of the draft. Tarik Skubal was a ninth-round pick in 2018, Joe Ryan was a seventh-round pick in 2018, Bryan Woo was a sixth-round pick in 2021, and Hunter Brown was a fifth-round pick in 2019. I might be speaking prematurely here, but Payton Tolle (a second-round pick in 2024) looked every bit of an ace during his major league debut.

I wondered if there was some secret metric that teams utilized to identify top-end talent in later rounds of the draft. While high velocity remains an important metric for evaluating pitchers, there are other factors to consider. Flame-thrower Stephen Strasburg's career was extinguished due to poor pitching mechanics, leading to wear and tear on his body from constantly throwing high-velocity pitches. Notably, after two UCL surgeries, Spencer Strider is struggling without his velocity. This emphasizes a crucial shift in evaluating pitchers. Factors beyond raw speed, such as long extensions, low release heights, and flat vertical approach angles, indicate a pitcher’s ability to miss barrels at the top of the zone with their four-seam fastball. 

Extension is a mechanical pitching statistic that measures the distance between the pitching rubber and where the pitcher releases the ball. Branch Rickey, former player and GM of the Brooklyn Dodgers, once remarked, “Baseball is a game of inches”. Every seemingly minuscule advantage influences whether or not a team makes the postseason, and ultimately, which team is awarded the Commissioner’s Trophy at the conclusion of the World Series. A pitcher with an extreme extension releases the ball closer to home plate to create the illusion of velocity. Balls thrown closer to home plate have less distance to travel, so to batters, they look faster than they appear. Baseball Savant quantifies this as "perceived velocity". 

In this case, size matters. While there are some exceptions (cough, cough Oneil Cruz, James Wood, and Aaron Judge), pitchers are the tallest guys on MLB rosters. Height correlates with longer extensions. Logan Gilbert is 6’5” and Tyler Glasnow is 6’8”. Both have 7.6 ft extensions, the longest in baseball, and their four-seam fastballs record a perceived velocity of 97.7 mph (95.4 mph actual) and 98.3 mph (95.8 mph actual), respectively. 

Rapsodo provides the following definition of release height: 

Quote

“Release height is measured as the vertical distance, in feet, between home plate and the pitcher’s vertical release point”.

While newer Statcast metrics, such as IVB, extension, velocity, etc., are frequently referenced by broadcasters and analysts, they rarely discuss vertical approach angle (VAA). Moreover, Baseball Savant doesn’t list VAA. I had to conduct some extra legwork to find where it’s publicly listed online. Fortunately, Chamberlain’s Pitch Leaderboard includes VAA. You might be wondering, what is vertical approach angle? VAA is a relatively new metric that measures the angle at which a pitch crosses home plate. I’m a visual learner, so I’ve included the following VAA graphic from Baseball Connect. 

[Image sourced from Baseball Connect]

Alex Chamberlain lists the following equation to calculate VAA in his Visualized Primer on VAA: 

vy_f = -sqrt(vy0² – (2 * ay * (y0 – yf)))
t = (vy_f – vy0) / ay
vz_f = vz0 + (az * t)
VAA = -arctan(vz_f/vy_f) * (180 / pi)

where, per Statcast’s documentation:

• vy0 = The velocity of the pitch, in feet per second, in y-dimension*, determined at y=50 feet. (*toward home plate)
• ay = The acceleration of the pitch, in feet per second per second, in y-dimension, determined at y=50 feet.
• y0 = 50 (“y=50 feet”).
• yf = 17/12 (home plate, converted to inches).
• vz0 = The velocity of the pitch, in feet per second, in z-dimension**, determined at y=50 feet. (**vertically)
• az = The acceleration of the pitch, in feet per second per second, in z-dimension, determined at y=50 feet.

As you can see, there’s a wide range of whiff rates depending on a pitcher’s repertoire. Steeper VAAs (>-5°) yield high ground ball rates and are thrown towards the bottom of the zone. These pitchers don’t throw fastballs as much, if at all. They throw pitches, e.g. sinkers and sliders, with downward movement to force the batter to swing over the pitch and induce weak contact.  Red Sox starter Brayan Bello sports a -8.1° VAA, the steepest VAA in baseball, and a 49.3% ground ball rate (82nd percentile). Like most ground ball pitchers, his sinker is his primary pitch. 

I initially was caught off guard seeing Tarik Skubal (-7.4°) and Garrett Crochet (-7.7°), the primary contenders for the 2025 AL Cy Young Award, post high VAAs. Skubal is less of a groundball pitcher (40.5% GB rate) than Crochet (49.2% GB rate), yet they still boast high whiff rates. Aces manage to generate outs and prevent runs, whether it's via ground balls or strikeouts. Moreover, their sheer dominance is rooted in not one, but several elite pitches, so they have some wiggle room with steeper VAAs.

On the other hand, flat VAAs (<-4°) are used to offset the swing plane of a typical uppercut hitter. Flat VAAs work best with long extensions and low release points to create ride and force the barrel to miss the ball. Guys with flatter VAAs (Joe Ryan, Bryan Woo, and Freddy Peralta) throw their four-seam fastball at the top of the zone and yield elite whiff rates,

Release height is the primary factor in determining a flat VAA for a four-seam fastball. I pulled data from the past two seasons (min. 1,000 pitches), displaying the relationship between four-seam fastball’s release height and VAA. For reference, it has an R-squared value of 0.506. 

Consider Minnesota Twins ace Joe Ryan. Upon first glance, Ryan’s four-seam fastball is unimpressive. It averages at 93.8 mph with 13.6” IVB, but Ryan’s 6.8 ft extension (79th percentile), low vertical release point (4.76 ft) and flat vertical approach angle (-3.9°) creates deceptive rise that causes the pitch to miss bats. Despite its subpar velocity and movement, his four-seamer ranks fifth among starters in strikeout rate (31.1%) and 10th in whiff rate (27.2%).

Ryan is a meticulous tinkerer with his mechanics, and Cody Christie from Talk Sox’s sister site, Twins Daily, has posted several excellent write-ups on his fastball over the past year. Ryan has added some velocity to his fastball. Three years ago, Parker Hageman, one of the founders of Twins Daily, posted an overview of Ryan’s fastball when it was averaging around 90 mph.

 

Since then, it's increased to 93.6 mph. On August 13, Ryan recorded the fastest pitch of his career, a 98 mph fastball to strike out Aaron Judge. Even without elite velocity, Ryan’s four-seam fastball is a force to be reckoned with; it’s generated +20 run value, tied for first with Bryan Woo’s, another starter with an illusory fastball thrown at a flat VAA (-3.7°). If Ryan manages to increase its velocity on a consistent basis, the rest of the league had better watch out.

When watching old videos of Payton Tolle in college, I couldn’t help but draw comparisons to Woo, the current ace of the Mariners. At 6’6”, Tolle is larger and throws left-handed, but their fastballs are very similar, dominating the upper part of the strike zone.

Like Woo, Tolle’s four-seam fastball has gained significant velocity since he was drafted, jumping from the low 90s to a 96.2 mph average in his major league debut. He posted a 5.52 release height and elite 7.5 ft (99th percentile) extension, which factored into his flat vertical approach angle and made his fastball exceptionally effective. Tolle recorded a 37.5% whiff rate on the pitch. While his overall command and secondaries need some refinement, his debut showcased plenty of promise.

Payton Tolle's Major League Debut
Pitch	Pitch%	VAA	Avg Velo	IVB	HB	Ext	Whiff%
Four-seam fastball	59.5%	-4.2°	96.2 mph	16.3"	-6.2"	7.5 ft	37.5%
Cutter	23.8%	-5.9°	90.1 mph	9.0”	2.0”	7.4 ft	16.7%
Changeup	9.5%	-6.9°	90.1 mph	1.7”	-8.0”	7.5 ft	66.7%
Slider	4.4%	-8.2°	84.5 mph	-6.5”	5.2”	7.4 ft	33.3%

So, why does VAA matter? An elite fastball is a solid foundation for a pitcher to build their arsenal. Teams can utilize VAA to identify overlooked pitchers whose four-seam fastballs have the potential to perform better than their initial projections. However, it takes two to tango. Players must be receptive to new information, willing to take input from their coaching staff, and implement changes effectively. Joe Ryan, Bryan Woo, and Payton Tolle have meshed well with their respective organizations’ coaching staffs and player development initiatives. In the worst-case scenario, things might not work out well between the team and the player. It was apparent that Walker Buehler was not receptive to the Red Sox’s pitching staff. On the flip side, teams must communicate effectively with their players. Otherwise, suggested changes might not be implemented. 

At the end of the day, VAA is another metric to consider when evaluating a pitch’s effectiveness. This article primarily reviewed VAA and four-seam fastballs, and there’s definitely more research to be conducted on the relationship between VAA and other pitch types. VAA depends on several interconnected factors, including the location of the pitch, a pitcher’s extension, and their release height. To effectively leverage a flat VAA for four-seam fastballs, a pitcher must be able to consistently throw the pitch up in the zone and utilize a long extension and a low release height.

Hopefully, mainstream baseball databases will soon include VAA in the near future, so armchair analysts like you and me can keep exploring these metrics.

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[TedYazPapiMookie]

Seeing metrics related to pitching creates a false knowledge of the future of a pitcher.  What makes Tolle interesting after a small sample size is his ability to locate at a high speed.  We've seen him locate and we've seen him not locate.  Immediately he reminded me of EROD.  EROD always had above average stuff and no ability to consistently deliver his stuff.  The same will be true for Tolle.  When he consistently delivers his stuff to the planned locations, he'll be outstanding.  When he can't locate, he'll get clobbered.  All the pretend metrics may look impressive, but it's all a bunch of crap that fans fall in love with as if it has meaning.  The fascination with measurements and simulation is so mind boggling to old school baseball fans and mind numbing to the baseball generation that grew up on video games.

Metrics give uneducated fans a basis for trying to discuss baseball with actual baseball fans who know the game and don't have to pretend they understand the game because they can quote meaningless estimates generated by theoretical mathematicians not baseball fans.

[illinoisredsox]

2 hours ago, TedYazPapiMookie said:

 When he consistently delivers his stuff to the planned locations, he'll be outstanding.  When he can't locate, he'll get clobbered. 

Wow, what penetrating analysis.  This statement can be made about every pitcher who’s ever lived.  The great ones can locate consistently with occasional blips. The poor ones can’t locate consistently with occasional times when they can.

At least the reply didn’t rival War and Peace for word count.

[mvp 78]

Another great piece from Maddie. 🏆

Lucky to have so many great writers here! 

[Kimmi]

Great article Maddie.  Thanks for the legwork and the analysis.

You can bet that teams are leaning on their analytics departments to provide them with this type of insight.

[Brandon Glick]

This piece was just nominated for a SABR award!! Congrats to Maddie!

https://sabr.org/latest/announcing-finalists-for-2026-sabr-analytics-conference-research-awards/