Glossary

Hitting

  • Exit Velocity: The speed of the ball off the bat, measured in MPH.
  • Launch AngleThe angle, measured in degrees, of the ball coming off the bat. 10 degrees or less are ground balls, 10-25 degrees are line drives, 25-50 degrees are fly balls, and 50 degrees and up is considered a pop-up.
  • Spray Angle: the horizontal angle that the ball leaves the bat. A negative number represents a ball hit to the left of second base, and a positive number represents a ball hit to the right of second base.

Pitching

  • Spin Rate: The rate at which a baseball rotates per minute. The average Fastball Spin Rate during the 2019 MLB season was 2250rpm..
  • Release Extension: The horizontal distance from the pitching rubber to the point where the pitcher releases the ball.
  • Release Dispersion: Release dispersion is a measure of how closely concentrated a pitcher’s release points are. A higher value represents less consistency, whereas a value of 0 shows all the pitches were released at the same point. A sample of MLB data showed that pitchers at that level have a dispersion of approximately .2, but this varies greatly between individual pitchers.
  • Spin Efficiency: The ratio of transverse spin to total spin. This ratio excludes the gyroscopic (slider, bullet, football) type of spin.
  • Vertical Approach Angle: The angle at which a pitch crosses home plate, measured in degrees. This number is always negative because it is impossible to make a baseball “rise”. Fastballs typically cross the plate at a -5 ⇒ -6 degree angle, and curveballs typically cross the plate at a -7 ⇒ -8 degree angle.
  • Induced Vertical Break: Distance, measured in inches, between where the pitch actually crosses the front of home plate height-wise, and where it would have crossed home plate height-wise if had it traveled in a perfectly straight line from release, but affected by gravity.

 Plate Discipline

  • Whiff %: Total swinging strikes divided by total swings by a hitter (or swings against a specific pitcher). The average Whiff % in the big leagues in 2019 was 24.3%.
  • Chase %: A “Chase” swing is a swing at a ball located outside of the strike zone. Chase % is calculated by dividing Swings outside the strike zone by total swings taken. The average Chase % in the big leagues in 2019 was 28.3%.
  • Chase Contact %: Is the metric that measures the contact rate of a batter of pitches out of the strike zone. The average Chase Contact % in the big leagues in 2019 was 59.6%.
  • Zone Swing %: Is the total number of swings at pitches inside the strike zone. This is calculated by dividing total swings at pitches in the strike zone by total swings. The average Zone Swing % in the big leagues in 2019 was 66.1%.
  • Zone Contact %: Is the percentage of swings that make contact with the ball with pitches in the strike zone. The average Zone Contact % in the big leagues in 2019 was 82.9%.

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