Key Takeaways: Defensive Metrics and Analysis

Quick Reference Card

Traditional Statistics Limitations

Stat What It Misses
Tackles Context (depth, opportunity)
Sacks Volatility, team effect
Interceptions Luck, target volume
Yards Allowed Opponent quality

EPA Allowed

EPA Allowed = EP after play - EP before play

Good defense = Negative EPA allowed

Rating EPA/Play Allowed
Elite < -0.10
Good -0.10 to -0.05
Average -0.05 to 0.00
Below Avg > 0.00

Success Rate Allowed (Stop Rate)

Stop Rate = Plays where offense failed / Total plays × 100

Success thresholds (from offense perspective): - 1st down: 40% of distance - 2nd down: 50% of distance - 3rd/4th: 100% of distance

Benchmarks: | Rating | Stop Rate | |--------|-----------| | Elite | > 60% | | Good | 55-60% | | Average | 50-55% | | Below Avg | < 50% |

Pass Rush Metrics

Pressure Rate:

Pressure Rate = Pressures / Dropbacks × 100
Rating Pressure Rate
Elite 35%+
Good 30-34%
Average 25-29%
Below Avg < 25%

Sack Rate:

Sack Rate = Sacks / Dropbacks × 100
Rating Sack Rate
Elite 8%+
Good 6-8%
Average 5-6%
Below Avg < 5%

Sack Conversion:

Sack Conversion = Sacks / Pressures × 100

Normal: ~20-25% Above 30%: Likely regression coming

Pass Rush Win Rate (PRWR)

PRWR = Pass Rush Wins / Pass Rush Snaps × 100
Rating PRWR
Elite 50%+
Good 45-49%
Average 40-44%
Below Avg < 40%

Coverage Metrics

Completion Rate Allowed:

Comp% Allowed = Completions / Targets × 100
Rating Comp% Allowed
Elite < 55%
Good 55-60%
Average 60-65%
Below Avg > 65%

Passer Rating Allowed (NFL Formula):

def passer_rating_allowed(targets, comp, yards, tds, ints):
    a = max(0, min(((comp/targets*100 - 30) / 20), 2.375))
    b = max(0, min(((yards/targets - 3) / 4), 2.375))
    c = max(0, min((tds/targets*100 / 5), 2.375))
    d = max(0, min((2.375 - (ints/targets*100 / 4)), 2.375))
    return ((a + b + c + d) / 6) * 100
Rating Passer Rating Allowed
Elite < 70
Good 70-85
Average 85-95
Below Avg > 95

Run Defense Metrics

Yards Per Carry Allowed: | Rating | YPC Allowed | |--------|-------------| | Elite | < 3.5 | | Good | 3.5-4.0 | | Average | 4.0-4.5 | | Below Avg | > 4.5 |

Stuff Rate:

Stuff Rate = Rushes ≤ 0 yards / Total rushes × 100
Rating Stuff Rate
Elite > 20%
Good 17-20%
Average 14-17%
Below Avg < 14%

Opponent Adjustment

Adjustment Factor = Avg Opponent EPA / League Avg EPA
Adjusted Stat = Raw Stat / Adjustment Factor
Factor Schedule
> 1.20 Very Hard
1.05-1.20 Hard
0.95-1.05 Average
< 0.95 Easy

Position-Specific Evaluation

Edge Rusher Key Metrics: 1. Pass Rush Win Rate (45%+ = elite) 2. Pressure Rate (12%+ = elite) 3. Time to Pressure (< 2.5s = elite) 4. Double Team Win Rate

Cornerback Key Metrics: 1. Completion Rate Allowed (< 55% = elite) 2. Passer Rating Allowed (< 70 = elite) 3. Yards per Target (< 6.0 = elite) 4. Playmaking (INTs + PBUs)

Linebacker Key Metrics: 1. Run Stop Rate 2. Coverage Grade 3. Tackle Rate (tackles/opportunities) 4. Blitz Productivity

Safety Key Metrics: 1. Coverage Grade 2. Run Support Grade 3. Range (tackles 20+ yards downfield) 4. Turnover Generation

Essential Formulas

Comprehensive Defensive Grade

def defensive_grade(data):
    # Component scores
    pass_score = grade_pass_defense(data)  # 45% weight
    run_score = grade_run_defense(data)     # 30% weight
    sit_score = grade_situational(data)     # 15% weight
    to_score = grade_turnovers(data)        # 10% weight

    return (pass_score * 0.45 + run_score * 0.30 +
            sit_score * 0.15 + to_score * 0.10)

Key Concepts Summary

What Each Metric Measures

Metric Measures Best For
EPA Allowed Overall effectiveness Unit evaluation
Pressure Rate Pass rush success Pass rush evaluation
PRWR Individual rush ability Player evaluation
Comp% Allowed Coverage tightness DB evaluation
Passer Rating Combined coverage DB evaluation
Stuff Rate Run defense at LOS Front 7 evaluation

Stability of Metrics

More Stable Less Stable
Pressure Rate Sack Rate
PRWR Sack Totals
Yards per Target Interceptions
YPC Allowed Fumble Recoveries

Common Pitfalls

  1. Tackle totals without context - Depth matters more than volume
  2. Raw sack numbers - Pressure rate is more predictive
  3. Ignoring schedule - Opponent adjustment is critical
  4. INT totals - Highly volatile year-to-year
  5. Yards/Points allowed - Lacks situational context

Evaluation Framework

Team Defense Evaluation

  1. Calculate EPA/play allowed - Overall effectiveness
  2. Separate pass/run defense - Identify strengths
  3. Analyze situational - 3rd down, red zone
  4. Adjust for opponents - Context is critical
  5. Check turnovers - Add randomness caveat

Individual Defender Evaluation

  1. Identify position-specific metrics
  2. Calculate rates, not totals
  3. Compare to positional benchmarks
  4. Adjust for role and opportunity
  5. Consider scheme fit

Chapter 9 Summary

  1. Traditional stats have significant limitations
  2. EPA allowed provides context-aware evaluation
  3. Pressure rate beats sack rate for predicting future success
  4. Coverage metrics should be target-based
  5. Opponent adjustment is essential for accurate evaluation
  6. Position-specific analysis requires different frameworks
  7. Composite grades combine multiple dimensions