This week I wanted to look more in-depth at the aerodynamic fingerprints of different pitches, particularly sinkers. A sinker is a two-seam fastball that drops as it approaches the batter and is frequently pounded into the ground by a hitter. Pitchers who throw good sinkers tend to rely heavily on the pitch and don't need to worry as much as a "normal" pitcher about changing speeds.

The whole point of changing speeds and throwing different pitches is to induce weak contact (or strike-outs), but when a sinker is thrown properly, a batter generally makes poor contact and hits it on the ground anyway. Armed with detailed information about each pitch, I looked at three sinkerballers and made some interesting observations about each of them.

Derek Lowe was the first pitcher I studied. Here's a graph showing the breaks of Lowe's three pitches, a sinker, slider and curveball over parts of two starts this season, on 4/13 and 4/24. Lowe pitched well in both these outings, allowing four runs over 16 innings of work.

One thing that immediately jumps out to me in the chart is the consistent horizontal break, compared to a non-spinning pitch, of his sinker. Most breaks that I have seen, both horizontal and vertical, have been much more spread out, similar to how the vertical break of his sinker appears. As I mentioned in my previous article with regard to release point, I'm not sure whether consistency is necessarily a good thing for pitchers. While having a consistent break on a pitch would seem to help the catcher receive the ball and give the pitcher confidence that he knows where he's throwing to, it would also help a hitter who could prepare for only one type of break on the sinker. If Lowe is always this consistent though, it hasn't really been a problem for him.

Another thing to notice on this chart is Lowe's curveball. He throws the pitch infrequently, but both the horizontal and vertical break (compared to a pitch with no spin) are around zero inches. According to the data his curve ends up almost exactly where a pitch with no spin would, and with a speed of 82 MPH, appears to be a meat-ball. Fortunately for Lowe, this isn't the case. The pitch has some movement, measured by the length of the break (defined as the measurement of the greatest distance between the trajectory of the pitch at any point between the release point and the front of home plate, and the straight line path from the release point and the front of home plate) which is 11.5 inches, the greatest of any of his pitches. The hump in Lowe's curveball creates enough deception to allow him to throw it on occasion without getting burned.

Colorado's Aaron Cook is another sinkerball artist. While I had 200 pitches over two starts for Lowe, I only had 103 pitches from Cook, all of them from his start on 4/8. This was a fantastic start for Cook, despite a no decision, as he pitched 9 innings and allowed only one run. Here's a chart showing the break on his pitches in that start.

Comparing the horizontal break on Cook's sinker to Lowe's reinforces how consistent Lowe was. The chart on the right shows Lowe's start on April 13, and even though Lowe had a more consistent break (a tighter bunching of clusters) for all of his pitches compared to Cook, the horizontal break of the sinker was especially consistent. Cook's curve has a break pattern that is typical of a curveball, with the pitch ending up lower than would be expected with a non-spinning pitch. Compared with Lowe's curve, the vertical break is on the left of the horizontal break in the chart, which I believe is a graphic indicator of a curveball. Despite these differences in the way their sinkers moved, Lowe and Cook both had excellent starts in the games I examined, so there are clearly multiple ways to skin a cat here.

I wanted to look at another NL West sinkerball, Brandon Webb, but Gameday has only tracked 83 pitches for Webb so far this season, leading to a much murkier chart than Lowe's or Cook's. There are three basic clusters of pitches, but there is also a collection of scattered points, which I'm unsure how to identify. Even the clusters I'm able to identify are much further apart than most pitchers I've examined. I have noticed some obvious inconsistencies in the data so far, mostly involving the speed and release point, so this break information could be wrong too. The pitches I was unable to identify could be another pitch that Webb throws, but I'd like to see another start worth of information from Webb before I form an opinion on his pitches or their movement.

Excluding Webb, the only other true sinkerball I had a reasonable amount of data for was Carlos Silva. I have information on 110 pitches that Silva threw over two different starts, 4/07 and 4/18, and when I created his chart, I found he has only thrown two pitches, a sinker and change up. Because of the inconsistent way Gameday collected data from those two starts, Silva could have thrown other pitches that weren't collected by Gameday. However, I think if he did have another pitch, he would have thrown it more than a couple of times over 110 random pitches.

The table below shows some interesting information about the three sinkers examined. The numbers measuring the pitches are all median values as opposed to mean values. Silva relies on his sinker more than Cook or Lowe, but his sinker has less of a downward break, measured by both the vertical break compared to a non-spinning ball and the length of the break, which is the number I used to describe the hump in Lowe's curveball. Silva's average sinker ended roughly nine inches higher than a non-spinning pitch would have, while Lowe's and Cook's pitches ended roughly four inches above the imaginary terminus. The backspin on a pitch is what causes it to end up higher than a non-spinning pitch would, so Silva's sinker must have more backspin than Lowe's or Cook's. When a hitter hits a sinker with too much backspin, he still hits a grounder, but as Dan Quisenberry famously put it, "in this case, the first bounce is 360 feet away."

An average sinker from Silva reached its high point roughly seven inches above an imaginary line from release point to home plate, compared to roughly nine inches for Lowe and Cook, leading to a smaller vertical drop for Silva. These observations seem to jive pretty well with reality, as Lowe and Cook are both thought to have better sinkers than Silva, and one thing that could lead to a more effective sinker is getting more downward movement on the pitch.

Name   Sinker%   Speed    Horizontal Break   Vertical Break    Break Length
Lowe   65%       90 MPH   -10.75"            3.68"             9.00"
Cook   68%       93 MPH   -10.02"            4.60"             8.30"
Silva  77%       93 MPH   -10.74"            9.39"             6.85"

For the sake of comparison, and to make sure I wasn't drawing conclusions about a trend that didn't exist, I wanted to get the average values for several four-seam fastballs and see how they compare to these sinkers. For this, I used Matt Morris and Jake Peavy. The table below shows the same information as above, but for Morris' and Peavy's fastballs.

Name     Fastballs  Speed    Horizontal Break   Vertical Break    Break Length
Morris   79         89 MPH   -9.01"             9.47"             6.70"
Peavy    104        95 MPH   -10.32"            8.49"             6.60"

With all the usual warnings about a small sample size, the sinkers appear to be different from the four-seam fastballs, which is a great finding. The fastballs have different horizontal and vertical breaks and a much smaller break length relative to the sinkers. One interesting thing was the similarity of Silva's sinker to the four-seam fastballs. Silva struggled in spring training this year with controlling his sinker and maintaining the sink on the pitch, so perhaps this is numerical evidence of those struggles. Either that, or that's just how Silva's sinker typically behaves, and his normal sinker is different that Lowe's or Cook's.

I was very pleased to discover that pitches were able to be identified using just the horizontal and vertical break values from Gameday. In the future, I'd like to continue looking at different pitches and see the differences between say, Barry Zito and Rich Hill's curveballs, or Johan Santana and Cole Hamels' change up. The fact that there was a distinct difference between a four-seam fastball and a two-seam fastball gives me hope that sifting through the database to find the different types of pitches a pitcher throws is an attainable goal.