By Jake Mintz
FOX Sports MLB Writer

A grunt, a whir, a whiff, a pop, a shake of the head, a confident strut from a mustachioed man in tight pants, a dissatisfied trudge back to the dugout.

Rinse and repeat.

That’s usually how things go when Spencer Strider, the Atlanta Braves’ superb rookie hurler, unleashes his trademark four-seam fastball. Ask any catcher who has been given the responsibility or privilege of handling that fastball, and they’ll all use the same word: electric. That’s fitting; electricity moves at 90% the speed of light, just like Strider’s triple-digit fastball.

Drafted in the fourth round out of Clemson in 2020, Strider’s ascension to the top of MLB’s pitching ranks has been just like that heater: sudden, unexpected, up in your grill before you even had a chance to notice. After spending most of April and May of this season shining in Atlanta’s bullpen, the 23-year-old moved to the rotation for his first start on May 30.

Since then, he has hurled 82 1/3 innings across 16 starts with a 3.06 ERA. Strider has K’d a mind-boggling 121 hitters in that time, good for a league-leading (among starters) 13.23 strikeouts per nine innings. Opposing batters are hitting a meek .190 against the right-hander, the sixth-lowest mark among starters in the league.

Strider has been devastatingly dominant, unbelievably untouchable, a crucial part of a Braves rotation that has received underwhelming production from Charlie Morton and Ian Anderson, two stalwart members of last year’s title-winning group.

And he has done it all with just two pitches: that whizz-bang fastball and a ridiculously sharp slider that probably deserves its own appreciation post. Technically, Strider has a changeup, too, but he uses it almost exclusively against lefties (9.6% of the time) and rarely throws it to right-handed hitters (only nine times this season).

Chances are Strider is going to throw you a fastball or a slider, as he has thrown one of those two a whopping 94.5% of the time. It’s incredibly unusual for a starting pitcher to be so dominant with just two pitches. Only one starter in MLB, Cincinnati‘s Hunter Greene, has been more reliant on his top two pitches this season (94.9% fastball/slider), but Greene has struggled to the tune of a 5.26 ERA.

Greene is also the only starting pitcher with a higher average fastball velocity than Strider (98.8 mph vs. 98.3 mph). So why has Greene scuffled while Strider has blossomed into one of the NL’s best starters, especially when both dudes boast elite velocity? How has Strider carved up opposing hitters without a real third pitch?

It’s about more than just speed, my dear friends.

Before the advent of modern motion-tracking technology, fastballs were mostly evaluated by three main components.

1. Velocity: How fast is the pitch moving?

This is the most objective and obvious metric. Once smart people invented radar guns, fastballs were mostly judged by raw speed.

2. Command/control: How well can the pitcher locate the pitch?

Pinpointing a fastball up, down, in and out is incredibly difficult and allows pitchers to succeed with less velocity. Go watch late-career Greg Maddux or Mark Buehrle or any great Ryan Yarbrough appearance.

3. Horizontal movement: How much does the pitch move side-to-side?

Two-seam fastballs, sinkers and cutters that moved more horizontally were considered tougher to hit than a “flat” fastball, a phenomenon we now know to be mostly false.

Thanks to contemporary gadgets such as TrackMan and Statcast, we now know that a fastball’s effectiveness is about way more than those three attributes. Spin, vertical movement and vertical approach angle (VAA) also play important roles in how hitters react to fastballs. 

Strider’s heater is a perfect example. Yes, he has elite velocity, which is undeniably a crucial part of his profile, but other hurlers have chucked cheddar, too. Strider’s fastball, however, grades out extremely well in a variety of other vital metrics, particularly vertical break and VAA.

Strider has elite amounts of vertical break on his fastball, so let’s talk about what that means. Gravity impacts every fastball differently, depending on spin and velocity. The average heater drops 15 inches between the pitcher’s hand and the plate. Strider’s drops only 11 inches. That lack of downward movement means hitters tend to swing under Strider’s fastball, a sensation amplified by his quite low VAA.

VAA is a relatively new concept in pitching evaluation — so new, in fact, that it’s exceedingly difficult to find MLB VAA data online. But ask any big-league front-office member, and they’ll tell you how fundamental the metric has become within the game. FanGraphs’ Alex Chamberlain has done a lot of research into VAA, and I highly recommend checking out his work. 

Here’s how VAA works:

Essentially, no fastball travels in a perfectly straight line, parallel to the ground. If it did, the ball would fly well over the batter’s head. Instead, pitchers throw from the elevated surface of the mound, and then gravity pulls the ball downward, toward the earth. This means every pitch — for purposes of this discussion, every fastball — crosses the front of the plate at an angle.

At first glance, differences in fastball VAA among MLB pitchers might look relatively minor. Among starters, Houston‘s Cristian Javier has the lowest VAA, at 3.9 degrees, while Detroit‘s Michael Pineda has the highest, at 6.1. Strider sits at 4.4 degrees. But those small differences can have a huge impact, as two otherwise identical fastballs thrown at the top of the strike zone, one with a smaller VAA and one with a larger VAA, will appear different to a hitter’s eyes.

A variety of components can alter a pitcher’s VAA, including velocity, release height and vertical movement. Also, shorter pitchers such as Strider tend to have lower VAAs because they release the ball closer to the ground. Strider is listed at exactly 6 feet, but he has an average pitch release height of 5 feet, 7 inches. That’s an enormous difference from a guy such as Pineda, who has an average pitch release height of 6 feet, 5 inches.

All of this matters because hitters have been conditioned to expect a fastball to drop some incremental amount between the mound and the plate. So when a less vertically inclined pitcher such as Strider — who has good spin and elite vertical movement and releases the ball closer to the ground — throws a heater at the top of the zone, batters will swing under the baseball more often than not.

Put simply, the most effective pitches act differently than hitters expect them to. That’s a fundamental commandment of baseball. A curveball that looks like a fastball is more likely to generate a swing-and-miss or weak contact. The same dynamic works for a low-release, high-carry, elite-velocity fastball such as Strider’s.

It’s a big part of why the rookie has succeeded to such a shocking extent while relying almost exclusively on two pitches. His triple-digit heat, awesome slider and bulldog mentality on the mound are huge, too, but Strider’s fastball is much more than raw gas. 

And now, the next time you see a hitter helplessly flail at one of Strider’s four-seamers at the top of the strike zone, you’ll know why.

Jake Mintz, the louder half of @CespedesBBQ, is a baseball writer for FOX Sports. He’s an Orioles fan living in New York City, and thus, he leads a lonely existence most Octobers. If he’s not watching baseball, he’s almost certainly riding his bike. Follow him on Twitter @Jake_Mintz.

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