A new PITCHf/x chart

For a long time, I've been frustrated by spin movement (Magnus effect) charts because they don't genuinely show how much a pitch actually moves. These charts perfectly demonstrate how the spin of the ball changes its path, but they don't show how velocity adds a vertical element to the pitch's movement.

Take this chart for example. These are the pitches thrown by Texas Rangers LHP Derek Holland during September and October of last season.

Texas Rangers LHP Derek Holland's pitches.

Texas Rangers LHP Derek Holland's pitches.

Even though they are much slower pitches, Holland's change ups are located in the exact same place on the graph as his fastballs. If his fastball and change up start with the same trajectory, the change up will always cross the plate lower than the fastball. I wanted to capture this on a chart, so I put gravity back into the equation.

Using Gameday's physics data (initial position, initial velocity, acceleration), I calculated how long each pitch was in the air. Keep in mind, though, that PITCHf/x starts at 50 from the plate and ends just in front. The mapped data covers only about 48 1/2 feet.

With the flight time for each pitch, I calculated the drop caused by [sea-level] gravity. After converting this number from feet to inches, I added the vertical spin movement. Here's how it turned out:

Texas Rangers LHP Derek Holland's pitches on the gravity chart.

Texas Rangers LHP Derek Holland's pitches on the gravity chart.

Success. The change ups now appear below his fastballs. The chart reflects not only gravity's effect on a pitch, but it also helps separate pitches by velocity, making identification a little bit easier.

This chart does not replace virtualizations by any stretch of the imagination, but I think it does show how different two pitches can be from each other even when spin movement alone can't show it. Taking this a step further could lead to a "hitter's decision" chart that would represent how different the pitches look at a certain time or distance from the plate.

The gravity charts are now available for all pitchers in TexasLeaguers.com's PITCHf/x Database.

[[Update: On April 24, 2010, the Spin Movement w/Gravity charts were updated to reflect gravity's effect from y = 40 to y = 1.417. This change was made based on the information that can be found at Alan Nathan's PITCHf/x site: MLB Extended Gameday Pitch Logs: A Tutorial]]

Texas Rangers Prospects: Derek Holland and Zach Phillips

Derek Holland. The 2006 25th round draft-and-follow signee snuck up on a lot of people last season, even himself. Holland himself can not explain how he gained 5 mph on his fastball during the season. A lot of pitchers will experience a dip in velocity in their first full years as a professional as the long season wears them down, but Holland got stronger. At the end of the season in the Texas League playoffs, Holland allowed only 1 run over 20.2 innings (0.44 ERA) across 3 starts. He won't be sneaking up on anyone this year. He'll start the year in the Oklahoma City rotation, but he could be in Arlington sooner rather than later. Zach Phillips. Another left-handed draft-and-follow pitcher, Phillips struggled in his first full season assignment despite a wonderful short-season debut. In his second attempt at the Midwest League, Phillips stood out as one of the best pitchers. 2008 was another let down year, but if the pattern holds, Phillips could be primed to re-breakout.
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