Like Josh Kalk, I’ve been thinking about ways of automating the pitch classification process, although he’s much further along that process than I am. One thing I have wondered is whether such a system can ever be developed that will handle all pitches from all pitchers, or whether we will have to restrict it to mainstream pitchers and pitches only. So I’ve been thinking about pitchers who might be exceptions to various rules that seem to apply well to everyone else.
Take Chad Bradford, for instance. Could a pitch classification system handle a pitcher who throws underhand? He plays in a home park, Baltimore, that doesn’t have the PITCHf/x system running, but we have 188 pitches recorded for him in other parks, and that seems to be enough to figure out his repertoire.
The scouting information on Bradford couldn’t be much muddier for a guy who doesn’t throw very many different pitches and uses the same basic delivery for all of them. One scouting report says he throws a fastball, a slider, and an occasional changeup. The Sporting News says he “throws in the high 80s and has a solid changeup and curveball.” Another article (of which I seem to have lost track) said he threw a two-seam sinking fastball. The Washington Post says he throws an 83-mph fastball, a slider, and a changeup. The Post article is well worth reading if you’re interested in Bradford. Everyone seems to agree he has three pitches, but they can’t agree what they are. Surely we can tell if we dive into the data we have.
Let’s start with what is becoming my traditional pitch classification graph, pitch speed versus spin direction. (As usual, I have normalized the start_speed parameter to y0 = 50 feet.)
I’ve not labeled the slow breaking pitch in the graph because, as we will discuss later, it’s name is not so clear. I have color-coded his three pitches and circled the groupings, and now I’ll go through the process I used to determine those groupings and the pitch types.
There are two pretty obvious groupings, one containing the fastballs and the other some sort of slower breaking pitch. There are several questions to answer. First, are the multiple pitches hiding in the cluster on the upper right, and if so, what are they? Second, what is the 65-70 mph pitch? None of my usual secondary graphs were very illuminating on these questions.
To help answer the first question, I went to another pair of graphs I like to see, the same speed vs. spin direction plot from above but split out for right-handed and left-handed hitters.
The first thing I notice is that lefties don’t get many of the slow breaking pitches in the lower left corner of the graph, and righties don’t see pitches slower than 76 mph on the right side of the graph. That implies that there are at least two distinct pitches in our grouping on the right side, since I see no reason to believe Bradford would purposefully throw his already-slow fastball even slower to lefties on occasion. Most probably this is a changeup. We can’t tell from this graph whether righties also see some changeups from Bradford or whether 76 mph is really the cutoff between fastballs and changeups.
For that, we move to another plot that exposes a limitation in our data. This graph shows Bradford’s pitch speeds (normalized to y0 = 50 feet) throughout the season, recorded when the Orioles visited a park equipped with PITCHf/x and Bradford happened to pitch. The x-axis lists the pitch id number from my database, but that corresponds closely to time, with pitch #1 at the beginning of the season and pitch #637,220 occurring on September 12.
Here we can see on a game-by-game basis that Bradford clearly throws three different speeds of pitches. Our overall speed data is being clouded by two games in Boston on July 31 and August 1, with pitch speed on average 3.5 mph slower than in other parks. Fenway Park’s PITCHf/x system is the source of all sorts of measurement errors, so this does not come as a surprise.
Now that we’ve separated the three groups of pitches, can we tell what they are? First, it’s reasonable to classify the mid-speed pitch as changeup since it has similar spin to the fastball only thrown a little slower. But is the fastball a regular four-seam fastball or a two-seam “sinking” fastball as some people suggested? And is the breaking pitch a slider or a curveball?
As an aside, in terms of pitch classification algorithms, do we really care what the names of Bradford’s pitches are or how he pronates his wrist? Shouldn’t a mathematical description of how the pitch moves be sufficient? I think the answer to the latter question is probably yes, but pitch classification can be interesting beyond just the search for a universal classification system. It’s interesting to learn about a particular pitcher’s approach, and for that description, it helps to know what the pitcher is attempting from his perspective.
How do we determine whether a fastball is a four-seamer or a two-seamer? The classic four-seamer, if thrown from the 12 o’clock position, would have only backspin, which would show up on our graph as a spin direction of 180 degrees. If the pitcher drops down to a 3/4 delivery, the four-seamer gets a little sidespin component, and the spin direction shifts to the neighborhood of 210 degrees. For example, we saw Volquez’s four-seam fastball right in this area, in the range from 200-220 degrees, and Papelbon’s four-seamer was in a similar range of spin directions, 195-225 degrees.
The two-seam fastball is thrown with the fingers along the seams, with the middle finger applying pressure to the ball to produce sidespin. If the two-seamer were thrown from the 12 o’clock position, we would expect to see a spin direction greater than 180 degrees by an amount dependent on how much sidespin the pitcher applied to the ball. From a 3/4 delivery, the spin direction would shift over to a greater angle by another 30 degrees or so. Greg Maddux’s two-seamer had spin directions in the range 215-265 degrees (a wide range consistent with his reputation of varying the movement on his fastball), Papelbon’s two-seamer was at 210-235 degrees, and Volquez’s two-seamer was at 220-245 degrees.
For an pure underhand pitcher with a delivery from 6 o’clock, the classic four-seam fastball with pure backspin (now switched to pure topspin by the change in delivery) would have a spin direction of 0 degrees (equivalent to 360 degrees). For a more realistic delivery from 5 o’clock, which appears to be consistent with pictures I can find of Bradford’s motion, the spin direction would shift back by about 30 degrees to 330 degrees. If Bradford were applying pressure to the ball to produce the sidespin of a two-seamer, that would tend to move the spin direction back toward 360 degrees because of the direction that the human wrist pronates. Instead, we see a spin direction of 295-330 degrees, consistent with a delivery between 5 and 6 o’clock and little or no sidespin applied to the ball. Therefore, I conclude he is throwing a four-seam fastball.
This conclusion squares with one we could have made via logic alone, without regard to the data. Pitchers generally attempt to throw their fastball as hard as they can, which is accomplished with the four-seam grip. They use different grips and accept slower speeds for the purposes of movement or deception. Because of his underhand motion, Bradford gets plenty of sink on his fastball without needing to sacrifice speed to put sidespin on the ball. Here’s the chart of vertical and horizontal movement.
His fastball sinks 5 to 12 inches, which is just incredible–almost as much downward break as a Barry Zito curveball! His fastball also moves in on the hands of a right-hander by 7 to 13 inches, which is comparable to the best two-seam sinkers thrown overhand from guys like Brandon Webb and Derek Lowe. You wonder why right-handers can’t hit this guy? My guess is that’s why. And it’s all attributable to the spin direction, which in turn comes from the underhand delivery, and not to the speed of the pitch, which is only in the low 80′s.
Finally, we come to the last question for this post: Is that a curve or a slider? It has the horizontal break of good curveball, and sometimes a little more. It has a vertical break somewhere between a typical slider and curveball. Which is it? We already know that Bradford’s unorthodox delivery can significantly affect the movement on a pitch. For the answer, we turn back to the spin direction graph. Bradford’s breaking pitch checks in with spin directions in the range of 75-130 degrees. That’s not too different than an overhand curveball delivered from the 1 o’clock position, although not a perfect fit.
A curveball with pure topspin delivered from the 12 o’clock position has a spin direction of 0 degrees. Dropping down to the 1 o’clock position shifts the spin direction to 30 degrees. However, the pronation of the actual human wrist can’t deliver pure topspin to the ball without also imparting some sidespin that pushes the spin direction up to higher angles. For example, Maddux’s curve lands in the 50-100 degree range of spin direction, Volquez throws his curve at 35-80 degrees, and the few curves we saw from Papelbon ranged from 40-80 degrees.
A theoretical underhand 6 o’clock curveball delivered with pure topspin (now switched to pure backspin by the change in delivery) would have a spin direction of 180 degrees. Coming back up to the 5 o’clock position would shift the spin direction back up to 150 degrees. The sidespin imparted by pronation would move us back toward 180 degrees; however, and we don’t see Bradford’s breaking pitch around 180 degrees.
So Joe Slider, our blog turns its lonely eyes to you.
Woo, woo, woo…
What’s that you say, Kerry Robinson?
Slidin’ Joe has left and gone to the plate.
Hey, hey, hey…hey, hey, hey!
Sorry for that, I needed a distraction. This post is getting a little long in the tooth. I now return you to “The Slider Teaches Johnny to Pronate”, already in progress…
A pitcher throwing a typical slider overhanded applies sidespin in the opposite direction of a two-seamer, as if it were trying to become a topspin curveball, which you might say it was. In the process, it also gets a significant spin component around the direction of travel, which we ignore in terms of affecting the break of the pitch. The significant sidespin of the slider would put its spin direction around 90 degrees in theory, 120 degrees if it’s thrown from 1 o’clock, but in reality the pronating wrist ends up turning more toward the backspin of the fastball than the topspin of the curveball, and our typical slider ends up at slightly higher angles than 90 or 120 degrees. Checking back on our previous pitch classifications, a Greg Maddux slider falls in the range of 130-175 degrees, and Papelbon’s slider is in the range 140-190 degrees.
If Bradford were throwing a slider from the 5 o’clock position, at approximately what angle would we expect to see it spin? If he were throwing from the 6 o’clock position and getting pure sidespin on a slider, we’d expect it to have a spin direction of 270 degrees. Moving his delivery toward 5 o’clock moves the spin direction on the slider toward 240 degrees. But then the wrist action tends to pull it back toward the fastball, maybe in the neighborhood of 280 degrees. Huh. We don’t see Bradford’s breaking pitch centered anywhere close to that.
In fact, it’s centered around a spin direction of 100 degrees, closer to the 180 degrees we’d expect from a submarine curveball than the 280 degrees we’d expect of a submarine slider, but still not a great match for the curveball. In fact, it seems to have a strong screwball component, which makes some sense out of the movement we see on the vertical/horizontal break, but makes no sense to me in terms of why Bradford would throw a screwball or screwball-like pitch rather than a curveball/slider. Screwballs are hard to throw; they’re hard on your arm, which makes no sense for Bradford, who already has to deal with back pain from his submarine delivery. Nobody reports Bradford throwing a screwball. Maybe this is because it moves more like a traditional overhand slider or curve, but more likely it’s because he doesn’t throw a screwball.
Maybe some of you can help me by finding an error in my calculations or reasoning or pointing me to a more authoritative scouting report on Bradford. Until then, I’ll have to leave his third pitch as a mystery.
Update: I’ve done more reading on Bradford and the underhand delivery, and I’m finding some support for the idea of Bradford throwing a screwball. Most people don’t call it that because it doesn’t move like a screwball from an overhander, but it appears I may not be as off base as I thought I was.
From the Sporting News: “Chad Bradford is a submariner with a tough slider and a circle changeup. Because of his delivery, Bradford essentially twists his hand to the left on each pitch, turning the ball over–almost a screwball-type action.”
Some of you who know more about pitching motions and grips might be able to make something out of the pictures in Chris O’Leary’s analysis of Bradford.