Context of the Statistics

Understanding Baseball’s Tracking Revolution

From traditional box scores to millimeter-accurate radar tracking, modern metrics quantify aspects of baseball that were once invisible. Explore the key definitions, mathematical formulas, and interactive distributions below.

Understanding the metrics used throughout this analysis helps clarify how Major League Baseball has evolved. Here is what each statistic measures and why it matters in modern baseball.

⚡ Strikeouts per 9 Innings (K/9)

  • What it is: The average number of strikeouts a pitcher records for every 9 innings pitched. \[\text{K/9} = \frac{\text{Strikeouts} \times 9}{\text{Innings Pitched}}\]
  • Why it matters: Strikeouts are the purest measure of pitching dominance because they take the defense and ballpark dimensions out of the equation. As pitchers gained access to pitch-tracking data, league-wide K/9 rose significantly.

💥 Hard-Hit Percentage (Hard-Hit %)

  • What it is: The proportion of batted balls hit with an exit velocity of 95 mph or greater. \[\text{Hard-Hit \%} = \frac{\text{Batted Balls with Exit Velocity} \ge 95\text{ mph}}{\text{Total Batted Balls}} \times 100\]
  • Pre-Statcast vs. Statcast measurement:
    • Pre-Statcast (2005–2014): Tracked by Baseball Info Solutions (BIS) scouts manually classifying contact into soft, medium, or hard trajectories through video analysis.
    • Statcast Era (2015–Present): Tracked automatically using radar and high-speed cameras to record exact exit velocities.
  • Why it matters: Exit velocity is the strongest predictor of offensive success. Balls struck at 95+ mph produce the vast majority of extra-base hits and home runs.

📡 The Statcast Context

Prior to 2015, player evaluation relied on box-score results and scout observation. The introduction of Statcast in all 30 MLB stadiums equipped teams with automated optical cameras and radar to track:

  1. Pitch movement & spin rate: Helping pitchers design sharper, higher-rising fastballs that create more swings and misses.
  2. Batted-ball trajectories (exit velocity & launch angle): Helping hitters optimize their swing paths to elevate balls with high exit velocities.

This data revolution explains why the league migrated diagonally toward higher strikeouts and harder-hit balls at the same time.

For full definitions and further reading on every tracking metric, explore the official MLB Statcast Glossary.