At the end of the 2006 season Major League Baseball installed new technology that traced the flight of the ball from the pitcher to the catcher. It functions by triangulating cameras that focus on an area just in front of the pitcher's mound. The cameras pick up the release of the ball at a spot that is 50 feet in front of the front edge of home plate. The cameras and system combine to measure the speed and acceleration of the ball. Using some physics it is then possible to calculate the trajectory of the ball and determine within one inch where it crosses the front of home plate. The result are graphics that look like this:
The above snapshot is taken from MLB.com's Gameday application and shows 5 different pitches and their path to the plate and final location.
Fortunately, the data persists beyond the pretty graphics and is accessible on MLB.com's website. It isn't readily accessible in that it is stored in XML files, but it can be downloaded and built into a database.
Armed with this data it is possible to look at a wide variety of variables and outcomes. Today though I'll just focus on pitch selection, velocity, and horizontal and vertical movement.
With regard to movement, it is measured as the number of inches that the ball moved compared to a ball without spin. In the case of a fastball, this is typically a positive number because the backspin on the ball prevents it from sinking as much (due to gravity) as a pitch without spin. So when you hear of a rising fastball, it isn't actually rising, it is dropping less than expected.
Horizontal movement then is a reflection of the side spin that is placed on the ball due to grip and angle of release. It is done from the point of view of the catcher so a negative value means the ball moves in on right handed hitters and a positive value means it would be tailing away.
With the long preamble out of the way we can look at the arsenals of the Tigers two flamethrowers.
Verlander is a 3 pitch pitcher with a fastball, change up, and curve. Jackson adds a slider to that mix, becoming a four pitch pitcher, but he rarely throws his curve.
Notice the difference in vertical movement. Verlander's curve ball has top spin causing it to drop precipitously. In the case of Jackson the side spin on the slider causes it to dive away from right handed hitters.
Verlander mixes his secondary pitches more than Jackson does. Jackson rarely turns to the change-up and even less frequently uses the curve. And while Jackson's change has considerable horizontal movement, it has a fairly small speed differential from his heater.
The most telling difference is probably in the fastball, which is ironic given the similarities in velocity. Jackson's fastball is quite straight compared to Verlander's with a horizontal movement half of what Verlander achieves. And that is probably the reason for Jackson's strike out rate of 5.3 per 9 innings.
For more information, visit Bill's writings on pitch f/x on his blog: http://www.detroittigersweblog.com/tag/pitch-fx/. Also, the Hardball Times has an extensive database of pitch f/x related information http://www.hardballtimes.com/apps/pitchfx_archive/.
Bill Ferris is a special guest contributor to TigsTown - you can read more from 'billfer' on his site Detroit Tigers Weblog