Tuesday, May 12, 2015

What is "Zone Score"?

The "Zone Score" is the sum of gifts and misses, as called by the home plate umpire, for a particular set of pitchers and hitters. This information is based on data provided by MLB Advanced Media's pitchf/x system, and calculated with the help of Brooks Baseball pitchf/x tool. Each games home plate umpire receives eight Zone Scores: two each (Standard and Adjusted), for pitching vs. left-handed and right-handed batters, for both teams.

The score is essentially the difference between strikes called outside the strike-zone (gift), and balls called inside the strike-zone (miss). The Standard score uses a strike-zone as outlined by MLB rules (width of home plate and from the bottom of the batter's knees to the midpoint of shoulders and belt) and the Adjusted score uses a strike-zone "generally accepted" based on the specifications of Mike Fast, a former writer for Baseball Prospectus. Generally speaking, the Adjusted Strike-Zone allows for slightly larger 'corners' for right-handed hitters, and a larger outside 'corner' for left-handed hitters, and is based on historical data. The Standard and Adjusted zone variations can be seen below, with the Adjusted zone shown with dashed lines. For more info on the Adjusted SZ and the information used to define it, see this article.

Standard and Adjusted Strike-Zones for RH (left) & LH (right) hitters.

For purposes of calculating our Zone Scores, pitches are considered "in" the zone if more than half of the plot touches the zone, and "out" of the zone if it does not.  For example:

Green circle: a pitch deemed "in" the zone. Red circle: a pitch deemed "out" of the zone. In this example, the ball considered in the zone would be a (miss), and the strike considered out of the zone would be a (gift).

Note: This method is under review and will eventually use a numerical standard based on raw pitchf/x data.

Each home plate umpire receives 8 Zone Scores:

  • (A) Dodger Pitching vs. LHH (Standard) - (DLSZ)
  • (B) Dodger Pitching vs. RHH (Standard) - (DRSZ)
  • (C) Opposing Team Pitching vs. LHH (Standard) - (OLSZ)
  • (D) Opposing Team Pitching vs. RHH (Standard) - (ORSZ)
  • (E) Dodger Pitching vs. LHH (Adjusted) - (DLAZ)
  • (F) Dodger Pitching vs. RHH (Adjusted) - (DRAZ)
  • (G) Opposing Team Pitching LHH (Adjusted) - (OLAZ)
  • (H) Opposing Team Pitching vs. RHH (Adjusted) - (ORAZ)

Based on these 8 Zone Scores, each home plate umpire receives 2 Game Scores. For more information on Game Scores, continue to this post.

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