October 30, 2013

Baseball ProGUESTus

Is Speed Enough?: A PITCHf/x Look at the Effect of Fastball Velocity and Movement

by Jonathan Hale

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Jonathan Hale has been using PITCHf/x to answer baseball questions all over the 'net since 2008. He once missed a Duane Ward curveball by three feet. You can read his writing about the Blue Jays or tell him what he should be analyzing next at The Mockingbird.

The obsession with velocity starts early: from the time a player is drafted, there is an almost ridiculous concentration on how hard he throws. Raw speed, more than anything else, is what turns heads and makes prospects fly up the rankings, even though it is widely accepted that velocity alone is not enough to get major league hitters out, and that there are plenty of pitchers who are very successful in the majors with underwhelming fastballs.

Once a player makes it to the majors and people have some first-hand experience with his pitches, we start to hear about the virtues of their moving, darting, or “electric” fastball. And often, starters break into the league at a certain velocity and then after a few years settle into throwing a few miles per hour slower, at which point the suggestion is made that they “backed off” their heater a little in order to get more movement (or “put a wrinkle on it”), which actually makes the pitch harder to hit. I’ve always wondered whether it was true that pitchers willingly give up their maximum velocity either for the sake of control, increased movement, or self-preservation.

Is there a sweet spot for velocity? Is there a point at which throwing harder gives diminishing returns? PITCHf/x should be able to provide some answers (although command is the missing ingredient). For the sake of the following, I am defining “movement” (or “break”) as the maximum distance between a given pitch and a straight line between where it was released and the catcher’s glove. Think of it as the “bend” on a pitch (or “break length” for those familiar with PITCHf/x terminology), which is not dependent on the specific left/right/up/down movement on a pitch.

Relationship between movement and velocity
First, let’s take a very simple look at the relationship between velocity and movement, just to confirm what seems likely: on average, pitches thrown harder will be straighter (or “flatten out”). Here is a heat map showing all the four-seam fastballs in the league since 2009, with velocity on the horizontal axis and movement on the vertical axis:

The most commonly thrown four-seamer in the majors is around 91 mph with a four-inch break, and in addition to a general downward trend (more speed = less movement), the maximum break that pitchers achieve decreases rapidly at speeds above 95 mph. There is simply nobody who throws in the high 90s who has the kind of eight-inch bend on their fastball that is achievable around 90 mph.

Now let’s look at the ability to miss bats with either movement or velocity. From here on, I am considering both four-seamers and two-seamers as “fastballs,” as there is so much overlap between the two—one man’s natural movement on his heater is another’s second pitch, and there is enough variation from one pitch to the next that often two-seamers that just don’t have a lot of action on them are classified as slower four-seamers.

When gauging the nastiness of a particular pitch, I like to take misses per swing, with all foul balls ignored since there is no way to differentiate between 400-foot drives inches foul and barely-contacted pop-ups. So for the following two graphs (done using conditional density in R for every pitch since 2009), we’re looking at how often someone decided to swing at a pitch and came up completely empty. First, here’s how movement affects swings-and-misses:

We see high values at the left side of this graph because pitches with that little movement are also going to be the fastest—but remember that pitches with movement between 8-10 inches don’t touch any of the higher velocities, and still we see their swings and misses climbing back up. Between 4-8 inches, though, there’s no real difference in miss percentage, which implies that adding a couple of inches from average movement is just not enough to start missing bats.

Now the same thing, looking at velocity:

Again, the bump at the bottom is likely because those are the really slow two-seamers with big bend. It makes sense that these two graphs are mirror images since we know there is an inverse relationship between speed and movement. Still, I think it’s interesting that the graph is flat from about 82 to 90 mph, at which point there is a steady rise in misses up to the very fastest pitches. I would have expected a steeper curve, with the high-90s especially being through the roof.

However, there is clearly a problem in pretending that we can isolate just movement or velocity when they are intertwined. So now here is a 3-d graph, with velocity “into” the graph, movement from side to side, and the height of the columns representing misses per swing:

In a way this is stating the obvious: velocity is the consistent key for missing bats, except for those at the slowest end of the range (i.e. fastballs with the most two-seam action), where the slowest and bendiest also get the job done (like a mini-changeup). But what I find interesting that high 90s fastballs with lots of movement are actually less effective at generating swings and misses than straighter ones.,

So often you hear about a guy overthrowing so that his fastball “flattens out” and is easy to hit, but at the highest velocities, literally “flat” fastballs are actually the best kind (although they probably get called “explosive” or “rising” instead). The problem with most guys overthrowing is probably something even worse than lack of movement: a lack of control, leading to pitches coming down the middle of the strike zone, where it just doesn’t matter how fast they are.

I used to see a lot of Brandon League during his time with the Blue Jays, and it always seemed strange that he would throw in the high 90s with incredible sinking action but didn’t strike out a lot of hitters, although he did put up phenomenal ground-ball rates. Which leads us to…

How velocity plus movement keeps the ball on the ground
Obviously, sinking or two-seam action induces grounders. Here is a look at what factors contribute to that effect, with movement on the horizontal plane and ground ball (per all balls in play) percentage vertically:

So while slightly-above average movement doesn’t help pitchers miss bats, it certainly helps them induce grounders. The part of the graph just above four inches of movement (league average) shows the steepest slope of increased ground balls, as opposed to a much smaller difference between pitches that bend six inches and 10. Even if you’re not a pure sinkerballer, a little downward action on your fastball goes a long way.

Now for how velocity affects ground ball rate:

Interestingly, although it’s a much lesser effect, high velocity also induces ground balls, despite the fact that harder fastballs are thrown up in the zone more often and tend to have less movement. It makes sense, though, that faster fastballs would be harder to “square up,” one of the reasons—aside from their ability to record strikeouts—why fireballers are more effective.

How movement plus velocity keeps the ball in the park
Clearly, more grounders is going to mean fewer extra-base hits, but what about home runs specifically? I can’t count the number of times I’ve heard that extremely hard-throwing pitchers are actually easier to hit homers off of because you can just stick your bat out and “let them do all the work.” As the saying goes, the harder a ball comes in, the harder it goes out.

First, the effect of movement on home runs per ball in play:

No surprise there; I would fall off my chair if sinkers weren’t harder to hit out of the park. Although again, notice how there’s no real change for below-average break, but right above the average of four inches there is a steady decline in homers. Now for velocity:

While fireballers might still be more prone to giving up homers if they can’t control their velocity, it’s not a result of the speed of their pitches. In fact, the opposite is true: even though they tend to be straighter and up in the zone, the more velocity a pitch is thrown with, the harder it is to hit it for a home run. Any possible result of having to “provide all the power” oneself is overshadowed by the fact that pitches with higher velocities are simply harder to square up.

Takeaways:

• Fastball movement doesn’t help pitchers miss bats. In fact, the opposite is true for the fastest pitchers.
• Fastball velocity translates to missed bats at a steadily increasing rate after 90 mph—there are no diminishing returns.
• Fastball movement significantly contributes to more grounders and fewer home runs.
• Fastball velocity also helps keep the ball on the ground and in the park.
• It’s not until around four inches of additional movement over a normal fastball that pitchers start missing bats, but they start inducing more grounders and allowing fewer homers right away.

If a pitcher doesn’t have the ability to put movement on his fastball up there with the best in the league, he’s not going to be able to use more movement to miss bats and increase his strikeout rate (and the opposite could be true). However, it doesn’t take much extra movement to start seeing dramatic changes in groundball and homer rate, and since break becomes increasingly elusive above 95 mph, you can see why pitchers (especially starters) who are not elite flamethrowers might want to take a little off their fastball for the sake of more movement (although this analysis doesn't prove that pitchers can increase movement by decreasing velocity; it simply shows that pitchers with slower fastballs tend to make their pitches move more). At extremely high velocities, though, who cares about movement? Bring the heat!