Know your PITCHf/x strike zone

One of the more useful additions to Pirates broadcasts over the past few years has been the Range Resources strike zone, which is the ROOT Sports version of the PITCHf/x strike zones seen at places such as Brooks Baseball and This allows broadcasters and viewers to see the location of a pitch relative to the strike zone, providing immediate feedback any time a home plate umpire makes a borderline call. This is very valuable, but it can also be somewhat misleading at times.

The main issue that can cause confusion is the strike zone included on the graphic. Since we do not know the size of the graphical strike zone, we still do not know for sure where a particular pitch was located. Further complicating things is the fact that the strike zone used by each source (ROOT, Brooks, Gameday, etc.) is just a little bit different. If we are analyzing a borderline pitch, where an inch or so in any direction could change everything, that makes a huge difference. So let’s compare some of the various graphics.

Let’s start with Rod Barajas’ at-bat in the third inning of Friday’s game against the Brewers. Barajas saw nine Randy Wolf pitches in the plate appearance, and ROOT showed the pitch locations right before he singled to left.

Since each of the other sources show the pitch locations from the catcher’s point of view, I flipped this image to make the different images easier to compare.

Now here are the pitch locations as shown by Brooks Baseball. (Note: This also shows the ninth pitch of the at-bat, which had not yet occurred on the previous graphic.)

Finally, here is the same at-bat on MLB Gameday.

Let’s start by looking at the Brooks Baseball image, because it is the only one that includes labels on the two axes. Brooks uses the rulebook width for the strike zone. The front of home plate is 17 inches wide. Because the PITCHf/x system measures the location of the center of the baseball, we also need to add about 1.5 inches for the ball’s radius. That leaves us with a rulebook strike zone that extends about 0.83 feet from the center of the plate in each direction, which is what the Brooks graphic uses. Brooks uses 1.5 feet for the lower boundary of the strike zone and 3.5 feet for the upper boundary. This is where things really get fuzzy, because the rulebook upper/lower limits change with each batter.

Now that we have an idea of where the Brooks strike zone is located, let’s see how it compares to the other two sources, starting with the third pitch of the Barajas at-bat. Once again, remember that each of these images is from the catcher’s viewpoint, since I flipped the ROOT image. On the Range Resources strike zone, the third pitch appears to be a borderline pitch that barely catches the inside corner. On the Brooks and Gameday images, it looks like the pitch is clearly inside the strike zone. Right off the bat, it seems like the ROOT strike zone has a bit of a tighter width than the other two sources. Additionally, take note of the border of the Gameday strike zone. It appears to show the rulebook strike zone, plus a second extended section that seems to represent a gray area, where pitches would be borderline calls. This extended border of the zone makes pitches 4 and 6 look fairly close, while they are clearly outside the zone on the ROOT and Brooks images.

Another thing to consider is the rulebook strike zone compared to the actual strike zone called by MLB umpires. Mike Fast did some great work on this topic at Baseball Prospectus before being scooped up by the Astros. In this article, he came up with a formula for estimating the actual strike zone based on a player’s height and whether he hits right-handed or left-handed. Here is how Barajas’ strike zone changes if we look at the actual zone instead of the rulebook zone. It does not change anything with the pitches in this particular at-bat, but it clearly could in another situation.

Let’s move on to Andrew McCutchen’s first inning at-bat against Wolf. If you remember, McCutchen tossed his bat aside after the fourth pitch and was surprised to hear it had been called a strike. Again, I flipped the ROOT image so it matches the other two, and the Brooks graphic is the only one that includes the fifth and final pitch of the plate appearance. In this situation, each pitch appears to clearly miss the strike zone on the ROOT graphic. The first pitch looks borderline on the Brooks zone, and pitches one, two and four all look very close on the Gameday image. This plate appearance is a good example of how a few inches can change everything.

One of the main things I wanted to learn from this analysis was where ROOT places the lower and upper limits of the strike zone on their graphics. By comparing the lower limits of the ROOT and Brooks strike zones relative to pitches one and four of this plate appearance, it appears that ROOT uses a lower limit that is just a bit higher than the one found on Brooks. Just eyeballing it, it appears to be located around 1.6 or 1.7 feet on the ROOT graphic.

Here is the Brooks graphic of McCutchen’s plate appearance with the actual strike zone from Fast’s formula included.

Finally, let’s see how things differ with a left-handed batter. Here are the graphics from Pedro Alvarez’s first inning strikeout against Wolf. All pitches of the at-bat are included in each graphic.

In this situation, there is a cluster of outside pitches that do not seem to be anywhere near the strike zone on the ROOT and Brooks images. Alvarez was called out on strikes on the fifth pitch of the at-bat. However, with the enlarged zone on the Gameday graphic, a couple of those pitches seem a bit less clear-cut. Here is the actual strike zone, using Fast’s formula.

League-wide, left-handed hitters see an average strike zone that is shifted significantly toward the outside corner. This is likely due to umpires setting up over the catcher’s right shoulder, making the outside corner difficult to see. While the final strike on Alvarez was pretty clearly outside the rulebook zone, it is a pitch that is frequently called a strike by major league umpires.

The last thing I want to look at is how the strike zone changes for different batters, particularly the lower and upper limits. On the image below, the black strike zone is the standard rulebook zone used by Brooks. The red zone is the estimated actual strike zone for a left-handed batter of Garrett Jones’ height, using Fast’s formula. The blue zone is Fast’s estimated actual zone for a right-handed batter of Josh Harrison’s size. As you can see, the typical strike zone varies greatly for different individual hitters. This would not be evident on the graphics shown by ROOT, Brooks or Gameday, as they use a standardized zone.

The Range Resources strike zone is very informative for fans watching the ROOT Sports broadcast of a game. But it is important to remain a bit open-minded on any borderline calls. Home plate umpires are far from perfect when calling balls and strikes, but they often deserve the benefit of the doubt on pitches in inconclusive locations.




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