Chapter 18: Key Takeaways - Team Defensive Analytics

Core Concepts Summary

1. Defensive Rating Fundamentals

• Defensive Rating (DRtg) = Points Allowed x 100 / Possessions
• Possessions = FGA + 0.44 x FTA - OREB + TOV
• Modern NBA league average: 110-114 DRtg
• Elite teams: <108 DRtg; Poor teams: >116 DRtg

2. The Defensive Measurement Challenge

3. Rim Protection Metrics

• DFG% at Rim: Opponent FG% on contested rim shots
• Contest Frequency: Rim shots contested per 36 minutes
• Deterrence Effect: Change in opponent shot selection when player is on court
• Elite rim protector: <55% DFG at rim + 8+ contests per 36

4. Perimeter Defense Reality

Variance in Opponent 3P Shooting:
- Individual defender: 10-15%
- Team scheme: 15-20%
- Shooter skill + random: 65-75%

Implication: Single-season perimeter stats are unreliable

5. Defensive Versatility Value

• Switch-everything schemes eliminate advantageous matchups
• Switchable = can guard multiple positions (1-4 or 2-5)
• Modern premium on versatility over single-skill excellence
• No defensive weak links is often better than one elite + one poor defender

Essential Formulas

Team Defense

Defensive Rating = (Points Allowed x 100) / Possessions

Possessions = FGA + 0.44 x FTA - OREB + TOV

Relative DRtg = Team DRtg - League Average DRtg

On-Off Differential = Team DRtg (Off) - Team DRtg (On)

Rim Protection

DFG% at Rim = Opponent FGM at Rim / Opponent FGA at Rim (when contested)

Rim Protection Frequency = Rim Contests / Minutes x 36

Points Saved per Game = Contests/Game x (League Avg Rim% - Player DFG%) x 2

Rebounding

Defensive Rebound % = DRB / (DRB + Opponent ORB)

Second Chance Prevention = Opponent ORB x Expected PPP per Second Chance

Shot Quality Defense

Expected FG% = Base Rate (by zone) + Contest Adjustment

Shot Quality Defense = Opponent xFG% (lower is better)

Luck Factor = Opponent Actual FG% - Opponent xFG%

Implementation Checklist

Setting Up Defensive Analytics Pipeline

• [ ] Data Collection
• [ ] Acquire play-by-play with shot locations
• [ ] Gather tracking data for contests and positioning
• [ ] Collect opponent statistics by game

• [ ] Track lineup and rotation data

• [ ] Basic Metrics Calculation

• [ ] Calculate team Defensive Rating by game
• [ ] Compute on-off differentials for all players
• [ ] Generate opponent shooting splits by zone

• [ ] Track defensive rebounding rates

• [ ] Advanced Analysis

• [ ] Build shot quality model (xFG%)
• [ ] Calculate rim protection metrics
• [ ] Create versatility scores

• [ ] Estimate RAPM (if sufficient data)

• [ ] Visualization

• [ ] Shot location charts (opponent shots)
• [ ] Heat maps of defensive coverage
• [ ] On-off comparison charts

• [ ] Trend analysis over time

• [ ] Reporting

• [ ] Generate defensive profiles by player
• [ ] Identify scheme strengths/weaknesses
• [ ] Compare to league benchmarks
• [ ] Create video integration lists

Common Pitfalls to Avoid

1. Over-relying on Outcome Metrics

Problem: Using opponent FG% to evaluate individual defenders Solution: Weight process metrics (contests, shot quality allowed) more heavily

2. Small Sample Conclusions

Problem: Judging perimeter defense from one season Solution: Require 2000+ minutes minimum; use multi-year samples

3. Ignoring Scheme Context

Problem: Comparing players in different defensive systems Solution: Adjust for scheme (drop vs. switch) and role

4. Neglecting Collaboration

Problem: Attributing team success/failure to individuals Solution: Recognize defense is fundamentally a 5-man endeavor

5. Assuming Skill from Results

Problem: Thinking low opponent FG% = good defense Solution: Separate shot quality creation from opponent shooting variance

Quick Reference Tables

Defensive Rating Benchmarks (Modern NBA)

Rim Protection Benchmarks

Individual Defensive Metric Reliability

Defensive Scheme Guide

Drop Coverage

Ideal For: Teams with elite rim protector, weaker perimeter defenders Strengths: Protects rim, reduces layups/lobs Weaknesses: Concedes pull-up threes, vulnerable to elite shooters Personnel Need: DPOY-caliber rim protector + decent perimeter recovery

Switch-Everything

Ideal For: Teams with multiple versatile defenders Strengths: Eliminates advantageous switches, disrupts actions Weaknesses: Post-up mismatches, size differential exploitation Personnel Need: All 5 players must guard 3+ positions competently

Blitz/Trap

Ideal For: Creating chaos, stopping elite ball handlers Strengths: Disruptive, forces turnovers, increases tempo Weaknesses: Leaves shooters open if rotation slow Personnel Need: Quick rotators, active hands, good communication

Zone

Ideal For: Hiding a weak defender, stopping penetration Strengths: Protects paint, reduces direct matchup exploitation Weaknesses: Vulnerable to good shooting, offensive rebounding Personnel Need: Smart defenders, good communicators

Application Scenarios

Scenario 1: Evaluating a Free Agent Defender

1. Gather multi-year on-off data
2. Calculate D-RAPM if available
3. Analyze scheme fit with your team
4. Review tracking metrics (contests, rim protection)
5. Watch video for process evaluation
6. Consider versatility for your scheme needs

Scenario 2: Game Planning Defense Against Opponent

1. Identify opponent's primary actions (PnR, ISO, etc.)
2. Analyze their efficiency by play type
3. Find their weak links (who to help off)
4. Design scheme to force worst options
5. Track shot quality allowed in-game

Scenario 3: Building a Defensive Roster

1. Identify your anchor (rim protector vs. switchable)
2. Ensure no severe weak links
3. Match personnel to scheme requirements
4. Prioritize versatility at wing positions
5. Consider transition defense ability

Scenario 4: Identifying Defensive Improvement Areas

1. Compare shot quality allowed to actual FG%
2. Identify high-frequency opponent actions
3. Find efficiency by zone/play type
4. Track transition frequency against
5. Analyze second-chance points allowed

Key Insight Summary

1. Defense is collaborative: Individual metrics have limited meaning without team context
2. Process > Outcome: Shot quality metrics are more stable than shooting percentages
3. Multi-year samples needed: Single seasons have too much variance
4. Rim protection still matters: But must be balanced with perimeter coverage
5. Versatility is premium: Modern offense hunts mismatches relentlessly
6. Scheme fit is crucial: Same player looks different in different systems
7. Video integration required: Numbers identify where to look; film shows why
8. Regular season != Playoffs: Scheme weaknesses get exploited more in postseason