In Search of the Sinker

Fastball, curve, change-up. That’s easy — oops, forgot one: slider.
Oh, then there’s the knuckleball, too. And the fastball isn’t really just one pitch, is it? Splitter,
cutter, two-seamer, four-seamer, sinker. Oy. There’s the 12-6 curve, the backdoor slider, the frisbee slider. The circle change, forkball and the palmball,
the screwball. What exactly is a knuckle-curve, anyway?

Lord knows there are many ways to throw a baseball and it’s hard for the average fan to keep this catalog of pitch types straight. There’s so much to know —
1) how does one throw these different pitches, 2) who throws what, 3) how do these pitches look to the batter, and so on. For those of a historical bent, like myself, you might
wonder who threw what first. You know, somebody ought to write a book on this subject, just write down everything we know about pitches and pitchers.

Of course, somebody has written that book, two guys named Bill James and Rob Neyer, authors of The Neyer/James Guide to Pitchers. I highly recommend it to
anybody who is interested in pitching, which is everybody, right? Actually, one thing that Neyer and James didn’t investigate is how the different types of pitches look
to the batter, and that’s what I’d like to tackle here. I want to look at how these different
pitches behave. What kind of movement do they have and how
fast are they typically thrown. Once I’ve gotten a feel for the data, I’m going to dig a little deeper on the the sinker, a pitch that
I have never understood very well.

I’m able to look at these things thanks
to the pitch data that MLB collects for its Enhanced Gameday
application.
Several writers on the Internet have already started to
delve into the wealth of information available: Joe P. Sheehan at
Baseball Analysts was the first (to my knowledge) and

Dan Fox (subscription required)

(Baseball Prospectus) and our own
John Beamer
have also worked with
the data. But, there is enough information available to keep at least a dozen analysts happy and I figure
the more people looking at it, the better.

Investigation of pitch types — does a slider really slide?

I’m going to focus on pitch speed and pitch movement, because different types of pitches will generally have different speeds or movements
or both. Pitchers also tend to be quite consistent in pitch speed and rotation, which gives rise to movement, from pitch to pitch (for a given pitch
type, of course). This is not true with pitch location, which pitchers have less control over.
Before we get into the nitty gritty, I need to define some terms that describe the movement of a
pitched ball.


I will refer to two different quantities that measure how much a ball
curves. The break of a pitch is the maximum distance between
the trajectory of a pitch and a straight line that connects the
starting and ending points of the pitch. In the graphic on the right,
the break is the length of the red line segment.

Movement, on the other
hand, is the term I use to describe how far a pitch moves compared to
a hypothetical pitch thrown without spin. Look at the graphic and
imagine that you are seeing an aerial view of a curveball. Had the
pitch been thrown without spin it would not have curved, but rather it
would have traveled along the blue dotted line. The length of the solid blue line
segment is the movement on the pitch. Each pitch has a horizontal and
vertical movement, which can be either positive or negative, depending
on which way the ball moves. There is only one break, though, and
being an absolute distance, is always positive.

Ok, let’s look at some pitches.

The plot on the left shows, for all 588 pitches thrown by Randy Wolf that
have been captured by Enhanced Gameday thus far, the pitch speed on
the vertical axis and the break on the horizontal axis. You
can easily see that Wolf threw three different types of pitches, at
three different speeds and breaks. In fact, if you look more closely,
you find that Wolf actually has a four-pitch arsenal. This can be seen
when you look at the graph on the right, which shows horizontal movement on
the x-axis and speed on the y-axis.
Now we see that the pitch thrown around 80 mph is actually two
different pitches with very different horizontal movement.

We still haven’t looked at the vertical movement yet; what I’d really like to
show is vertical movement, horizontal movement and pitch speed all on
the same plot. Since computer screens are still only two-dimensional,
though, I will show the following: vertical movement and
horizontal movements along the two axes, with the pitch speed
color-coded. The result for Wolf is shown on the right.

Let’s talk pitch type

Now we can start to examine this plot and and attempt to classify the different
pitch types. Let’s start with the green points: they are thrown
above 85 mph and in fact, these are fastballs. They typically have a
vertical movement of 10-15 inches and horizontal movement of 5-10
inches. Remember, these movements are as viewed by the catcher. Do
these numbers make sense? Hmm, vertical movement on the fastball
sounds right. But, since it’s positive, does that mean Wolf’s fastball
is actually rising, against the claims of physicists across the land?
No, because movement is measured relative to the same pitch thrown
without spin. Such a pitch will drop on its way to the plate. Wolf’s
fastball will drop about 10 inches less than the hypothetical spinless
pitch.

Does a fastball move horizontally, though? I have always thought that
a fastball is thrown with backspin, in which case there should be no
lateral movement. But this is only true for a strictly overhand
fastball, while almost every fastball is thrown with an arm angle that
is below straight-over-the-top. This imparts a sideways component to
the spin, which causes the ball to tail in to the batter (for a
right-handed pitcher and batter), i.e. it would have a negative
horizontal movement. For a lefty like Wolf, the horizontal movement is
positive.

Now, focus on the black points: these are thrown at less than 73 mph
and break down and to the left (from the catcher’s view): curve balls,
obviously. Aside from some trick pitches (knuckleball, underhand
pitches), anything thrown less then 75 mph is bound to be a curveball.
Now, the red points: you can see that Wolf throws two different
pitches in the high-70s, low-80s. The clump in the middle of the plot
are sliders: relative to the fastball, they break down and to the
left, just like the curves, but not as much. The red points in the
upper right of the plot are change-ups: similar movement to the
fastball, but thrown about 10 mph slower.

This business of identifying pitches strictly from the data is very exciting to an analyst, because it opens a multitude of
possible things to study: how a pitcher (or batter) fares on any given pitch type; how pitchers choose what pitch to throw, given the
batter, count and game situation, and so on.

The Mysterious Sinker

One pitch that has always fascinated me is the sinker.
I can remember thinking as a kid:
backspin gives the fastball that rise, side spin makes the curve ball
break sideways, so a sinker must be thrown with overspin. That didn’t
seem right, though, because 1) the “overspin” ball is just an overhand
curve and 2) seems like it would be difficult to throw a ball hard
&mdash and sinkers are thrown pretty hard — trying to throw it
with overspin.

It wasn’t until years later that I understood what a sinker really is:
it’s a fastball that has less vertical movement than a typical
fastball. Look, all pitches sink, in some sense. Every pitch ever
thrown has dropped due to the force of gravity. The lift
caused by the backspin on a fastball cannot overcome the force of
gravity. We saw above that Wolf’s fastball has a vertical movement of
10—15 inches. In other words, it drops 10—15 inches less
than an otherwise similar pitch without spin. A sinker, as we’ll see
in a minute, is a fastball that drops about 5—10 inches more
than a typical fastball.


The vertical movement for all fastballs (speed > 88 mph) in my pitch
database are shown in the graphic on the right (black points). The
green line shows the average relationship between pitch speed and
vertical movement. Fastballs that are well below the line are
“sinkers”. Those light blue points are the fastballs from a single
pitcher, can you guess who it is? Actually, it could be any number of
pitchers, but it happens to be Roy Halladay, who has a world-famous
sinking fastball and a nifty 55% ground ball percentage to go with
it.

So, which MLB pitchers have the greatest “sink” on their fastball? To
answer that question, I calculated the average vertical movement of
each pitcher’s fastball, which I defined as any pitch over 88 mph.
The following table shows the top 15 pitchers ranked according to
vertical movement.

Name                      Movement (in)
Meredith, Cla             -3.9
Moylan, Peter             -3.4
Feldman, Scott            -0.3
Halladay, Roy              2.9
Tavarez, Julian            3.0
Lowe, Derek                3.9
Loe, Kameron               4.1
Duckworth, Brandon         4.3
Wagner, Ryan               4.5
Cook, Aaron                4.6
Hernandez, Felix           4.7
Hudson, Tim                4.8
Webb, Brandon              5.1
Downs, Scott               5.3
Ortiz, Ramon               5.4

The interesting thing about making a list like this is that you often
turn up something new. I’m not sure I’ve ever even heard of Moylan or
Feldman, and it was interesting to see that they have two of the
sinkiest fastballs in baseball. Now, any pitcher whose fastball has a
negative vertical movement on average almost has to be a side-armer or
underhand pitcher. I know that Cla Meredith throws from the side, but I
had to go look at video of Moylan and Feldman to check their deliveries. My hunch was right: they both throw side-arm.

Just about every other guy on this list is known
as a sinkerball pitcher, and most of them have high groundball
percentages. Note that this is only a partial list, because not all
ballparks have the equipment necessary to produce the Enhanced Gameday
data. There are a lot of pitchers for whom little or no data is
available. Note that these pitches are sinking between 5 and 10
inches compared to an average fastball. That’s a lot, when you
consider that a batter will swing through a pitch if the center of the
bat misses the center of the ball by three inches.

I’m going to show you one last plot that demonstrates the connection between pitch vertical movement and
ground ball percentage. To make the plot on the right, I
took all fastballs that were put into play by the batter. I divided
this data set up into four subsets, depending on the vertical movement
of the pitch. The vertical movement of each subset is color-coded, from dark blue for the
“sinkiest” pitches, to yellow for the “rising” fastballs. Each bar in the graph shows the
percentage of a particular batted ball type (F, G, L and P mean fly
ball, ground ball, line drive and pop up) yielded in that subset of
the data.

You can see clearly that the groundball percentage varies
strongly with the vertical movement on the pitch. Obviously, the F and
P categories move in the opposite direction. Curiously, the line drive
rate is about the same for all vertical movements.

But how do you throw the damn thing?

This is all very nice, but I must admit, it doesn’t really help
me understand how a sinker is thrown. Now, I realize that a
two-seam fastball will have less “rise” on it than a four-seamer will,
so maybe a sinker is just a two-seam fastball? It seems too easy,
doesn’t it? I mean, if it were just a case of holding the ball in
two-seam mode, anybody could throw a good sinker, right?

To get some insight on
that, I turned to the incomparable: Neyer/James Guide to Pitchers. In his article “The Mighty Fastball”, Bill James writes

However, while some pitchers could make a ball hop and some people could make a ball “sink,” there is no evidence of any major-league
pitcher, before 1950, doing both, or switching between one and the other. … Pitchers universally seemed to regard the movement of their fastball
as a gift from the heavens.

That’s curious, isn’t it? It seems like, before 1950 or so, the pitchers themselves didn’t know what made some fastballs sink and some hop. James goes
on to quote various real pitchers who didn’t understand why their ball happened to sink. Several speak of a “natural sinker.” James cites Curt Simmons as the first pitcher to throw both a rising and sinking fastball and then goes on to name several pitchers who had both pitches, including Fergie Jenkins and
Tom Seaver. This makes me wonder if today’s sinker-ball pitchers are consciously trying to throw a sinker, or it’s just a “gift from the heavens.”

Then, in the chapter “All the Pitches We Could Find,” Neyer and/or James give two possible descriptions of how to throw a sinker. The first is just a
two-seam fasty:

“Sinking fastball” is, today, synonomous with “two-seam fastball”. Basically, grip the ball along — as opposed to across — the two seams, and throw like hell.

But James/Neyer then relates a description of the sinker by long-time Dodger manager Walter Alston, who suggests, “In releasing the ball,
the pitcher has to turn the ball over at the last moment, placing more pressure on the index finger … Known as a sinker, it is a little more difficult to throw
than the rising fast ball because of the over-the-top wrist flip.”

Hmm, maybe Alston’s description is correct, but I imagine that this is a very subtle motion, especially when you consider that until 1950 or so, sinker ball pitchers were not even aware they were doing it.

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