Case Study 2: The Houston Rockets' "Moreyball" Era (2017-2020) - Team-Level Efficiency Optimization
Executive Summary
From 2017 to 2020, the Houston Rockets under General Manager Daryl Morey implemented the most extreme shot selection philosophy in NBA history. By virtually eliminating mid-range shooting and maximizing three-point attempts and shots at the rim, the Rockets demonstrated how shooting efficiency principles could transform team offense. This case study examines the analytical foundation of "Moreyball," evaluates its effectiveness through efficiency metrics, and analyzes both its successes and limitations.
Background: The Analytical Foundation
Expected Value Analysis
The Rockets' strategy derived from a fundamental expected value analysis:
| Shot Type | League FG% | Point Value | Expected Value |
|---|---|---|---|
| At Rim | 64% | 2 | 1.28 |
| Short Mid-Range (4-14 ft) | 40% | 2 | 0.80 |
| Long Mid-Range (14-3PT) | 40% | 2 | 0.80 |
| Three-Point | 36% | 3 | 1.08 |
| Free Throw (per 2 FTA) | 77% | 2 | 1.54 |
The mathematical conclusion was clear: mid-range shots were the least efficient option in basketball.
Morey's Philosophy
Daryl Morey articulated the approach:
"The 'mid-range dead zone' is real. Every mid-range shot is an opportunity cost. You're choosing a 0.80 expected value shot over a 1.08 or 1.28 expected value alternative."
This philosophy manifested in roster construction, player development, and real-time shot selection.
The Rockets' Shot Distribution Revolution
Evolution of Shot Selection
| Season | % Shots at Rim | % Mid-Range | % Three-Point | League 3PA Rank |
|---|---|---|---|---|
| 2014-15 | 28.1% | 18.2% | 32.4% | 2nd |
| 2015-16 | 27.9% | 13.4% | 38.9% | 1st |
| 2016-17 | 29.8% | 9.8% | 41.2% | 1st |
| 2017-18 | 31.2% | 6.4% | 42.3% | 1st |
| 2018-19 | 34.5% | 3.1% | 44.8% | 1st |
| 2019-20 | 35.8% | 2.8% | 45.2% | 1st |
By 2018-19, the Rockets had essentially eliminated mid-range shooting, with only 3.1% of attempts from that zone.
Comparison to League Average
| Zone | 2018-19 Rockets | 2018-19 League Avg | Difference |
|---|---|---|---|
| At Rim | 34.5% | 31.2% | +3.3% |
| Mid-Range | 3.1% | 15.8% | -12.7% |
| Three-Point | 44.8% | 34.1% | +10.7% |
The Rockets' mid-range rate was approximately one-fifth of the league average.
James Harden: The Moreyball Superstar
Shot Selection Alignment
James Harden's shot distribution exemplified the strategy:
2018-19 Season (36.1 PPG):
| Zone | FGA | FG% | Points | EV per Attempt |
|---|---|---|---|---|
| At Rim | 467 | 63.8% | 596 | 1.28 |
| Mid-Range | 68 | 39.7% | 54 | 0.79 |
| Three-Point | 1028 | 36.8% | 1134 | 1.10 |
| Free Throws | 858 | 87.9% | 754 | 0.88* |
*FT efficiency expressed per attempt, not per 2-FTA trip
Harden's Efficiency Profile
| Season | PPG | eFG% | TS% | 3PAr | FTr |
|---|---|---|---|---|---|
| 2016-17 | 29.1 | 52.4% | 61.3% | 47.8% | 53.2% |
| 2017-18 | 30.4 | 54.1% | 61.9% | 53.0% | 50.0% |
| 2018-19 | 36.1 | 54.1% | 61.6% | 56.9% | 47.5% |
| 2019-20 | 34.3 | 52.5% | 62.6% | 55.1% | 44.7% |
Despite leading the league in scoring at historic volumes, Harden maintained above-average efficiency.
The Step-Back Three-Pointer
Harden popularized the step-back three, demonstrating that even contested threes could be efficient:
| Step-Back 3PT Stats | 2018-19 |
|---|---|
| Attempts | 481 |
| Made | 168 |
| FG% | 34.9% |
| Expected Value | 1.05 |
At 34.9%, Harden's step-back three exceeded the expected value of a league-average two-pointer (1.04).
Team-Level Efficiency Results
Offensive Rating Performance
| Season | Rockets ORtg | League Rank | League Average | Difference |
|---|---|---|---|---|
| 2016-17 | 111.8 | 4th | 108.8 | +3.0 |
| 2017-18 | 112.4 | 3rd | 108.6 | +3.8 |
| 2018-19 | 113.8 | 2nd | 110.4 | +3.4 |
| 2019-20 | 112.9 | 6th | 110.6 | +2.3 |
The Rockets consistently ranked as one of the league's most efficient offenses.
eFG% Analysis
| Season | Team eFG% | League Rank | League Avg | Three-Point Impact |
|---|---|---|---|---|
| 2017-18 | 52.4% | 8th | 51.8% | +0.6% |
| 2018-19 | 53.1% | 7th | 52.5% | +0.6% |
| 2019-20 | 53.7% | 8th | 53.0% | +0.7% |
Key Observation: Despite league-leading three-point attempts, eFG% ranked around 7th-8th, not 1st. The volume-efficiency tradeoff appeared at the team level.
True Shooting Percentage
| Season | Team TS% | League Rank | Three-Point Contribution |
|---|---|---|---|
| 2017-18 | 57.0% | 3rd | High |
| 2018-19 | 56.7% | 7th | Very High |
| 2019-20 | 57.5% | 6th | Very High |
The Rockets' TS% exceeded eFG% substantially due to strong free throw drawing, particularly by Harden.
The Mathematics of Extreme Shot Selection
Marginal Efficiency Analysis
At extreme volumes, diminishing returns appeared:
Three-Point Efficiency by Attempt Rate:
| 3PA/Game | Rockets 3P% | Expected Decline |
|---|---|---|
| 30 | 38.2% | Baseline |
| 35 | 36.8% | -1.4% |
| 40 | 35.4% | -1.4% |
| 45+ | 34.1% | -1.3% |
As attempts increased, percentage declined, but expected value often still exceeded mid-range alternatives.
Break-Even Analysis
For the Rockets' strategy to be mathematically optimal:
$$3P\% \times 3 > 2P_{midrange}\% \times 2$$
With Rockets' mid-range rate at ~40%: $$\text{Break-even 3P\%} = \frac{2}{3} \times 40\% = 26.7\%$$
Even at their lowest three-point percentages (~32%), the Rockets exceeded this threshold.
The Variance Problem
Three-point shooting introduces variance:
Game-to-Game Standard Deviation:
| Metric | Rockets 2018-19 | League Average |
|---|---|---|
| 3P% Game SD | 12.4% | 9.8% |
| Points Game SD | 12.8 | 10.2 |
| ORtg Game SD | 14.2 | 11.5 |
Higher three-point volume increased game-to-game variance.
Case Within a Case: The 2018 Western Conference Finals
The Variance Manifests
Against the Golden State Warriors in Game 7, the Rockets' shot selection faced scrutiny:
| Metric | Game 7 | Series Average |
|---|---|---|
| 3PA | 44 | 42.3 |
| 3PM | 7 | 14.9 |
| 3P% | 15.9% | 35.2% |
| Final Margin | -9 | - |
The Rockets went 7-44 from three-point range, their worst performance of the season at the worst possible time.
Was the Strategy Wrong?
The Mathematical Argument For: - 15.9% was 2+ standard deviations below expected - Over 27 missed threes, expected value still: 0.159 * 3 * 44 = 21 points - Alternative mid-range attempts at 40%: 0.40 * 2 * 44 = 35 points
The Mathematical Argument Against: - Expected value analysis assumed normal distribution - Game 7 psychology may affect shooting percentages - Shot quality likely declined due to defensive pressure
Lesson: Variance Has Timing
The Rockets' approach was likely correct in expected value terms over a full season. However, playoff series with elimination games introduce timing risk that expected value analysis doesn't fully capture.
Supporting Cast Acquisition
Roster Construction by eFG%
The Rockets prioritized three-point shooting in roster construction:
| Player | Role | 3P% (Houston) | 3PA/Game |
|---|---|---|---|
| Eric Gordon | Starter | 36.0% | 7.8 |
| P.J. Tucker | Starter | 38.5% | 5.2 |
| Danuel House | Rotation | 36.6% | 4.8 |
| Ben McLemore | Bench | 40.0% | 4.3 |
| Austin Rivers | Bench | 35.2% | 3.4 |
Corner Three Specialists
The Rockets specifically targeted corner three-point shooters:
| Season | Corner 3PA | Corner 3P% | League Rank (%) |
|---|---|---|---|
| 2017-18 | 584 | 41.3% | 2nd |
| 2018-19 | 621 | 40.8% | 4th |
| 2019-20 | 498 | 42.1% | 1st |
Corner threes (shorter distance, 22 feet vs. 23'9") had higher expected value.
The Small-Ball Extreme: 2019-20
Going All-In
Mid-season 2019-20, the Rockets traded center Clint Capela and committed to extreme small-ball with 6'5" P.J. Tucker at center.
Shot Distribution Change (Pre/Post Trade):
| Zone | Pre-Trade | Post-Trade | Change |
|---|---|---|---|
| At Rim | 32.4% | 38.2% | +5.8% |
| Mid-Range | 3.8% | 2.1% | -1.7% |
| Three-Point | 44.2% | 46.8% | +2.6% |
Efficiency Results
| Period | ORtg | eFG% | TS% |
|---|---|---|---|
| Pre-Trade | 111.2 | 52.8% | 57.0% |
| Post-Trade | 115.1 | 54.8% | 58.2% |
The small-ball approach improved offensive efficiency substantially.
The Spacing Mechanism
With five players capable of three-point shooting: - Paint area more open for drives - Defensive rotations longer - Help defense compromised
At-Rim Efficiency:
| Lineup Type | Rim FG% | Rim EV |
|---|---|---|
| Traditional (with center) | 62.4% | 1.25 |
| Small-Ball (all shooters) | 67.8% | 1.36 |
Counterintuitively, removing the center improved rim efficiency through spacing.
Limitations and Criticisms
Playoff Performance Concerns
| Season | Regular Season ORtg Rank | Playoff ORtg Rank | Playoff Exit |
|---|---|---|---|
| 2017-18 | 3rd | 3rd | WCF (7 games) |
| 2018-19 | 2nd | 4th | WCSF (6 games) |
| 2019-20 | 6th | 8th | WCSF (5 games) |
The Rockets' offensive efficiency ranked lower in playoffs when defenses intensified and variance increased.
Three-Point Shooting Variance in Elimination Games
| Rockets Elimination Games (2018-20) | 3P% |
|---|---|
| Game 7 vs GSW (2018) | 15.9% |
| Game 6 vs GSW (2019) | 32.4% |
| Game 5 vs LAL (2020) | 27.6% |
The "Load Management" of Mid-Range
Some analysts argued eliminating mid-range entirely was suboptimal:
Counter-Argument: - Mid-range shots can be easier to generate - Some mid-range specialists (Chris Paul, Kawhi Leonard) shoot >50% - Eliminating options makes defense easier
Analytical Lessons
Lesson 1: Expected Value Works Over Large Samples
The Rockets' regular-season success validated expected value analysis: - Consistently top-5 offense - High efficiency despite extreme volume - Mathematical foundation proved sound
Lesson 2: Variance Matters in Small Samples
Playoff series (4-7 games) have insufficient sample size for expected value to dominate: - Bad shooting nights can end seasons - Opponents can adjust - Psychology affects performance
Lesson 3: Diminishing Returns Exist
At extreme three-point volumes: - Shot quality declines (more contested attempts) - Percentage decreases - Opponents specifically prepare for three-point defense
Lesson 4: System Fit Determines Individual Efficiency
Role players thrived in the Rockets' system:
| Player | Pre-Houston 3P% | Houston 3P% | Change |
|---|---|---|---|
| Eric Gordon | 33.8% | 36.4% | +2.6% |
| P.J. Tucker | 33.2% | 38.5% | +5.3% |
| Jeff Green | 32.4% | 36.8% | +4.4% |
Spacing and scheme created better shot quality.
Lesson 5: Trade-Offs Must Be Acknowledged
The Rockets accepted: - Higher variance - Playoff vulnerability - Defensive limitations (small-ball) - Roster inflexibility
These were conscious trade-offs, not oversights.
Legacy and Influence
League-Wide Impact
The Rockets' success influenced league-wide shot selection:
| Season | League Mid-Range Rate | Change |
|---|---|---|
| 2015-16 | 18.8% | Baseline |
| 2019-20 | 14.2% | -4.6% |
| 2022-23 | 12.8% | -6.0% |
The "Moreyball" Label
The approach became synonymous with analytics-driven basketball, influencing: - Roster construction league-wide - Youth player development - Media discourse about shot selection
Counter-Movements
Some teams explicitly rejected extreme approaches: - San Antonio Spurs maintained mid-range emphasis - Dallas Mavericks under Carlisle preserved diverse attack - Phoenix Suns built around mid-range star (Booker/Paul)
Conclusions
The Houston Rockets' Moreyball era (2017-2020) demonstrated both the power and limitations of applying shooting efficiency principles at scale:
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Mathematical foundation was sound: Expected value analysis correctly identified optimal shot selection zones
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Regular-season success was consistent: Top-5 offensive efficiency across multiple seasons
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Variance introduced playoff risk: Elimination games proved vulnerable to cold shooting
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System effects amplified individual efficiency: Role players benefited from scheme fit
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Extreme implementation had trade-offs: Flexibility, defense, and variance concerns were real
The era serves as a landmark case study in applying analytics to basketball strategy. The approach was neither wholly successful (no championship) nor a failure (consistently excellent offense). Its influence on league-wide shot selection trends will persist for decades.
Discussion Questions
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Did the Rockets correctly identify optimal strategy but fail in execution, or was the strategy itself flawed?
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How should expected value analysis be modified to account for playoff variance?
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What mid-range percentage would justify including mid-range shots in the Houston system?
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How did opponent adjustments affect the Rockets' efficiency over time?
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What lessons from the Moreyball era apply to basketball at other levels (college, high school, international)?
Data Sources
- NBA.com official statistics
- Basketball-Reference.com
- Cleaning the Glass
- Houston Rockets media guides
- ESPN Stats & Information
- Second Spectrum tracking data