The Importance of Fastball Shape

Velocity is all the rage these days, and why shouldn’t it be? It’s fun to see that third digit light up on a radar gun or show up on the scoreboard. And it’s happening more often than ever. From Opening Day through the weekend, eight pitchers combined for a total of 28 pitches over 100 mph, with Emmanuel Clase hitting the mark nine times out of the 11 cutting fastballs he threw on Sunday. It’s certainly exciting, but velocity isn’t everything. Yes, I want to know how hard someone is throwing when evaluating a pitcher, but my first question after that is what is the shape of the pitch?

A decade ago, scouts based their fastball grades almost entirely on velocity. Above-average velocity? Above-average fastball. But with the emergence of technologies like TrackMan, Hawkeye and Rapsodo, that one-to-one relationship has become a relic. There are pitchers who throw in the upper 90s who have average fastballs because of their shape and other intangibles; there are some with average velocity that are nonetheless plus pitches for the same reason. Because of this, the scouting scale has changed and is beginning to capture variables outside of just miles per hour. Some teams have begun asking their scouts to grade fastballs across three traits — velocity, movement and command. When I ran pro scouting with the Astros, I asked our scouts to capture velocity in their reports, but I wanted their fastball grade to reflect the effectiveness of the pitch in a more holistic way.

The best way to learn about fastball shape is first to think about what constitutes a normal shape. Sixto Sánchez has some of the best velocity in baseball, averaging a remarkable 98.5 mph with his four-seam fastball in 2020. It’s a plus pitch to be sure, but it also doesn’t play like you’d expect from a heater thrown 98-99 mph. Among the pitches in his arsenal, it’s the third most-likely to put away an opposing hitter, and it’s where he gives up his home runs. Why? Because in terms of fastball shape, it’s exceptionally normal. Here are Sánchez’s four-seam fastballs in 2020, as measured by horizontal and vertical movement:

I added a “line of normality” to show just that, as the 45-degree angle shows the normal amount of vertical and corresponding horizontal break on a fastball. As you can see, Sánchez’s four-seamer has just a smidge more rise (vertical) than run (horizontal), but for the most part, the cluster of pitches sits right on that line. These pitches are moving the way most fastballs move. More importantly, these pitches are moving the way hitters expect them to when they come out of his hand. The end result? A pitch that is easier to hit.

So how do pitchers gain fastball effectiveness beyond what the radar gun says? By creating differentiation between their fastball and the norm by utilizing either rise or sink. The further one can get from the norm, the more effective the pitch can be beyond just the pure speed. Hitters expect a fastball to behave a certain way out of the hand and when it doesn’t, regardless of the direction in which it deviates, it creates challenges in terms of making hard contact, or any contact at all.

To illustrate, there was a recent four-year run with the Blue Jays in which Marco Estrada was a pretty darn good starting pitcher. His best year came in 2016, when he had a 3.48 ERA over 176 innings and posted 2.7 WAR. He did this while averaging just 88.1 mph on his fastball. Of course his exquisite changeup was his signature pitch, but he still threw his fastball nearly 50% of the time. There are plenty of minor league arms with plus changeups who are doomed for the waiver wire due to a lack of giddy-up on their heater, so how did Estrada survive and even thrive at times? Simple: he deviated from the norm. Here are Estrada’s four-seam fastballs from that 2016 campaign:

Look at that. It’s glorious. That is a fastball that isn’t behaving at all how you’d expect out of the hand. Hitters are going to be under that all day despite the below-average velocity. Estrada’s changeup was great, but without a fastball shape like this, he would never be able to set it up in the big leagues, as a normally-shaped 88 mph would get whacked around the ballpark before he got the opportunity to start changing speeds.

One of the current rising champs is Cleveland reliever James Karinchak who takes a fastball shape similar to Estrada’s and then adds to the nastiness with plus velocity by averaging in the mid-90s with the pitch. As you can see from his 2020 pitch chart, the shape is far from typical:

More akin to Estrada in the prospect world might be 2019 Milwaukee Brewers first-round pick Ethan Small, who sits with well below-average velocity (89-92 mph) from the left side, but has fastball shape similar to Estrada’s, allowing the pitch the play up significantly.

These rising pitches can easily be spotted with naked eye. Watch them ride through the zone without the normal downward plane towards the plate, and when they generate swings-and-misses, bats are almost always under the ball. This is also the best type of fastball to elevate with, creating further difficulty in raising one’s bat plane to even make contact. They don’t come without risks: by being in a higher than expected place when they arrive at the plate, contact tends to be of the fly ball variety, and with fly balls come home runs.

Pitch data is the primary reason for the rising fastball exploding in popularity over recent years, but teams have historically also valued those who instead of working above the line of normality, create pitches below it by utilizing sink.

The type of backspin and arm angle used on risers is far more dramatic than what is physically possible with sinkers, but the charts show how someone known for being a groundball machine can achieve the title. Here’s Jack Flaherty in 2020.

The cluster is not nearly as dramatically placed as some of the big risers, but it’s easy to look at the chart and figure out why it works for Flaherty. The result is either a whiff or (because of the lack of significant differentiation from normal) the bat hitting the top of the ball and driving it into the ground.

If you are looking for more dramatic differentiation, there is Aaron Bummer, a true turbo-sink southpaw who offers both real velocity and some of the strongest sinking action around:

That shape and 96 mph are unhittable at times, but as Bummer often shows, that combination of velocity and movement can also be difficult to keep in the strike zone. So while extreme pitch shapes can greatly improved overall pitch effectiveness, they often come with greater difficulty in terms of location.

If you are looking for something downright weird, there’s always Tyler Rogers, who can survive in the big leagues while sitting in the low-to-mid-80s by coming in from down-under and creating a shape that is literally almost off the charts; it has to be, considering the speed.

The downside of the sinker is that for most pitcher, there isn’t the same dramatic deviation from normal one finds with rising fastballs. The closer to normal one is, the more contact there is going to be, and when there is contact, bad things can happen. Because the pitch has significantly more horizontal movement than four-seamers do, that different-than-normal shape is essential, otherwise one is intentionally moving the ball into the natural bat path of opposite-handed hitters, creating sizable platoon splits.

While looking at these charts and thinking about each associated pitcher, you might have already come to an important conclusion. A big part of these shapes is created by arm angles. Guys like Estrada and Karinchak are coming from nearly over the top. Sixto Sánchez has a classic three-quarters release, and that 45 degree arm angle creates shapes that match the 45 degrees of the dreaded line of normality. Sinkers tend to come from an angle lower than that, or in the case of Rogers, as low as you can go.

Shape provides an essential part of the answer as to why fastballs play above or below the number on the gun, and teams are still working on discovering new advantages from these realizations. Some clubs have started to look at a second differentiation factor, one that examines the difference between actual and expected shape. Not from the line of normality this time, but rather from the shape expected from the individual pitcher’s arm angle. Others are beginning to theorize that a pitcher with a lower arm angle who can create some backspin and rise — as opposed to the expected sink — could suddenly be in possession of a highly effective fastball.

Shape is important, but like every aspect of the game, there are no absolutes, which is what makes baseball so great. There is deception and tunneling and sequencing, and then there are the fastballs that just confound what the data tells us. Take a look at Max Scherzer:

Scherzer throws hard. Not crazy hard, mind you, but in the mid-90s. Obviously his fastball is really good, but in terms of shape, it’s quite normal. I’ve spent considerable time contemplating Scherzer and I’m don’t have a clear answer for you as to how he bucks the clear and obvious trend. But what is life without a bit of mystery? Just enjoy the magic sometimes.

When it comes to the overall effectiveness of power pitches, velocity drives the bus, but pitchers can find greater potency on their fastballs by adding unique shapes. At the end of the day, when the catcher puts one finger down, it’s good to be a little different.