Key Takeaways: Quarterback Evaluation

One-page reference for Chapter 6 concepts

Core QB Metrics

Metric Formula Meaning
EPA/Play Total EPA / Dropbacks Efficiency per attempt
CPOE Actual Comp% - Expected% Accuracy above average
ADOT Sum(Air Yards) / Attempts Passing depth
Success Rate Successful Plays / Total Consistency of positive plays

Quick EPA Reference

qb_stats = (
    pbp
    .query("pass == 1")
    .groupby('passer_player_name')
    .agg(
        dropbacks=('pass', 'count'),
        epa=('epa', 'mean'),
        cpoe=('cpoe', 'mean'),
        success_rate=('success', 'mean')
    )
    .query("dropbacks >= 200")
)

EPA Interpretation

EPA/Play Interpretation
> 0.20 Elite
0.10 to 0.20 Above average
0.00 to 0.10 Average
-0.10 to 0.00 Below average
< -0.10 Poor

CPOE Interpretation

CPOE Interpretation
> +4% Elite accuracy
+2% to +4% Above average
-2% to +2% Average
< -2% Below average

What EPA Captures

Included: - Yards gained - First downs - Touchdowns - Turnovers - Field position

Not Included: - Throw quality - Pocket presence - Pre-snap reads - Leadership

Supporting Cast Effects

YAC Adjustment:

team_yac = team_passes['yards_after_catch'].mean()
league_yac = all_passes['yards_after_catch'].mean()
receiver_contribution = team_yac - league_yac

Pressure Adjustment: - High sack rate → worse O-line - Adjust EPA for protection quality

Key Situational Analyses

Situation Filter
Early downs down <= 2
Third down down == 3
Red zone yardline_100 <= 20
Two minute half_seconds_remaining <= 120
Trailing score_differential < 0
Close game abs(score_differential) <= 7

Sample Size Guidelines

Metric Stabilization ~Games
Comp% ~150 attempts 4-5
CPOE ~200 attempts 6-7
EPA ~400 attempts 12-15
Int Rate ~800 attempts 2 seasons

Common Pitfalls

Pitfall Reality
High comp% = good Depends on depth
Volume = quality Efficiency matters more
One season proves skill Small sample variance
EPA isolates QB Includes cast effects

Evaluation Framework

1. Efficiency (EPA/play)
2. Accuracy (CPOE)
3. Style (ADOT, depth distribution)
4. Situations (3rd down, red zone, pressure)
5. Context (opponents, cast, scheme)

What Statistics Miss

  • Pre-snap reads and adjustments
  • Ball placement quality
  • Pocket navigation
  • Leadership and intangibles
  • Play-calling influence
  • Game management

Preview: Chapter 7

Next: Rushing Analytics — why traditional rushing stats mislead and how to properly evaluate running backs.