Chapter 13 Exercises: Goalkeeper Analysis

Overview

These exercises cover shot-stopping metrics, distribution analysis, sweeper-keeper evaluation, and comprehensive goalkeeper profiling. You will work with real match data to calculate, visualize, and interpret goalkeeper performance metrics.

Data Requirements: StatsBomb open data (accessed via statsbombpy)

Estimated Completion Time: 8-10 hours

Part 1: Shot-Stopping Fundamentals (Exercises 1-6)

Exercise 1: Basic Save Statistics

Calculate fundamental save statistics for goalkeepers in a match.

Tasks: a) Load a World Cup match and identify the goalkeepers b) Calculate total shots on target faced by each goalkeeper c) Calculate save percentage for each goalkeeper d) Compare these statistics between the two goalkeepers

Expected Output: Table showing basic save statistics for both goalkeepers

Exercise 2: Expected Goals Analysis

Analyze expected goals faced by goalkeepers.

Tasks: a) Calculate total xG of shots faced by each goalkeeper b) Compare xG faced to actual goals conceded c) Calculate goals prevented (xG - goals conceded) d) Interpret: Did either goalkeeper over- or under-perform expectations?

Expected Output: xG analysis table with interpretation

Exercise 3: Shot Quality Zones

Analyze shots faced by pitch zone.

Tasks: a) Categorize shots into zones (inside box central, inside box wide, outside box) b) Calculate save percentage by zone for each goalkeeper c) Calculate xG faced by zone d) Identify which zone presented the greatest challenge

Expected Output: Zone-based shot analysis matrix

Exercise 4: Save Difficulty Analysis

Examine the difficulty of saves made.

Tasks: a) For each save, record the xG of the shot b) Calculate the total "difficult saves" (xG > 0.15) c) Calculate average xG of saves made vs. goals conceded d) Create a visualization showing save difficulty distribution

Expected Output: Histogram of save difficulties with statistics

Exercise 5: Shot Outcome Breakdown

Create comprehensive shot outcome analysis.

Tasks: a) Categorize all shots by outcome (Goal, Saved, Saved to Post, Missed, Blocked) b) Calculate percentage distribution of outcomes c) Compare on-target shot outcomes between goalkeepers d) Calculate "shot conversion rate against" (goals / shots on target)

Expected Output: Shot outcome breakdown table and pie chart

Exercise 6: Goals Prevented Per 90

Normalize goalkeeper statistics to per-90 rates.

Tasks: a) Load multiple matches for a goalkeeper b) Calculate total xG faced and goals conceded c) Calculate goals prevented per 90 minutes d) Compare to league average benchmarks

Expected Output: Per-90 statistics with benchmark comparison

Part 2: Distribution Analysis (Exercises 7-12)

Exercise 7: Pass Completion Analysis

Analyze goalkeeper passing statistics.

Tasks: a) Extract all passes by the goalkeeper b) Calculate pass completion percentage c) Categorize passes by length (short <20m, medium 20-40m, long >40m) d) Calculate success rate by length category

Expected Output: Pass statistics table by length category

Exercise 8: Distribution Style Classification

Classify goalkeeper distribution style.

Tasks: a) Calculate percentage of long passes (>40m) b) Calculate ground vs. lofted pass ratio c) Analyze goal kick patterns specifically d) Classify style: "Launcher", "Builder", or "Balanced"

Expected Output: Distribution style classification with supporting metrics

Exercise 9: Progressive Distribution

Measure how effectively the goalkeeper advances play.

Tasks: a) Identify progressive passes (advances ball >10m forward) b) Calculate progressive pass percentage c) Calculate average progression distance on successful passes d) Identify the most common pass targets (by position)

Expected Output: Progressive pass statistics and target analysis

Exercise 10: Build-Out Play Analysis

Analyze goalkeeper involvement in build-out play.

Tasks: a) Count passes to defenders vs. midfielders vs. forwards b) Calculate success rate by target position c) Analyze pass timing (first-touch vs. controlled) d) Identify patterns in build-out sequences

Expected Output: Build-out analysis with pass flow visualization

Exercise 11: Goal Kick Patterns

Detailed analysis of goal kicks.

Tasks: a) Extract all goal kicks b) Calculate short vs. long goal kick ratio c) Analyze success rate by type d) Map goal kick end locations

Expected Output: Goal kick analysis with location heatmap

Exercise 12: Distribution Under Pressure

Analyze passing under defensive pressure.

Tasks: a) Identify passes made under pressure b) Calculate success rate under pressure vs. not under pressure c) Analyze how passing patterns change under pressure d) Identify risky passes in dangerous areas

Expected Output: Pressure analysis comparison table

Part 3: Sweeper-Keeper Metrics (Exercises 13-18)

Exercise 13: Actions Outside the Box

Analyze goalkeeper involvement outside the penalty area.

Tasks: a) Count ball recoveries outside the box b) Count clearances outside the box c) Count interceptions by the goalkeeper d) Calculate "sweeper actions per 90"

Expected Output: Outside-box action summary

Exercise 14: Defensive Line Support

Measure how the goalkeeper supports the defensive line.

Tasks: a) Analyze goalkeeper's average position during opponent possession b) Calculate distance from goal line during defensive actions c) Compare to team's defensive line height d) Identify patterns in sweeping behavior

Expected Output: Positioning analysis with defensive line comparison

Exercise 15: Cross Claiming Analysis

Analyze goalkeeper performance on crosses.

Tasks: a) Identify all crosses into the box against the goalkeeper's team b) Count successful claims (catches) by the goalkeeper c) Count punches and aerial clearances d) Calculate claim rate and success rate

Expected Output: Cross handling statistics

Exercise 16: Aerial Duel Analysis

Evaluate goalkeeper aerial ability.

Tasks: a) Count aerial duels won and lost b) Calculate aerial win percentage c) Analyze locations of aerial duels d) Compare to outfield defenders' aerial rates

Expected Output: Aerial duel statistics with comparison

Exercise 17: One-on-One Situations

Analyze goalkeeper performance in breakaway situations.

Tasks: a) Identify shots from counter-attacks or 1v1 situations b) Calculate xG of these shots c) Calculate save rate in these situations d) Compare to regular shot save rate

Expected Output: One-on-one analysis summary

Exercise 18: Rush-Out Timing

Analyze timing of goalkeeper advances.

Tasks: a) Identify instances where goalkeeper comes off line b) Analyze outcomes (save, goal, clearance) c) Calculate success rate of rush-outs d) Identify patterns in successful vs. unsuccessful rushes

Expected Output: Rush-out analysis with success factors

Part 4: Sample Size and Uncertainty (Exercises 19-24)

Exercise 19: Confidence Intervals

Calculate confidence intervals for goalkeeper metrics.

Tasks: a) Calculate raw save percentage from match data b) Calculate 95% confidence interval for save percentage c) Visualize the uncertainty range d) Discuss how sample size affects confidence

Expected Output: Save percentage with confidence intervals

Exercise 20: Bayesian Save Percentage

Implement Bayesian estimation for save percentage.

Tasks: a) Define an informative prior based on league averages b) Calculate posterior save percentage estimate c) Compare Bayesian estimate to raw estimate d) Show how the estimate evolves with more data

Expected Output: Bayesian analysis comparison chart

Exercise 21: Rolling Performance Metrics

Track goalkeeper performance over time.

Tasks: a) Load multiple matches for a goalkeeper b) Calculate match-by-match goals prevented c) Calculate 5-match rolling average d) Identify form trends and outliers

Expected Output: Rolling performance time series chart

Exercise 22: Stabilization Analysis

Investigate metric stabilization.

Tasks: a) Simulate goalkeeper performance over a season b) Track when save percentage stabilizes c) Track when goals prevented stabilizes d) Recommend minimum sample sizes for reliable evaluation

Expected Output: Stabilization analysis with recommendations

Exercise 23: Regression to Mean

Demonstrate regression to the mean in goalkeeper statistics.

Tasks: a) Identify goalkeepers with extreme first-half season performance b) Compare to their second-half performance c) Calculate regression effect magnitude d) Discuss implications for goalkeeper evaluation

Expected Output: Regression analysis with visualization

Exercise 24: Uncertainty Visualization

Create visualizations that communicate uncertainty.

Tasks: a) Create bar chart with error bars for save percentage b) Create distribution plot for goals prevented estimate c) Create comparison plot showing overlap in confidence intervals d) Discuss how to present uncertain data to non-technical audiences

Expected Output: Suite of uncertainty visualizations

Part 5: Comprehensive Applications (Exercises 25-30)

Exercise 25: Complete Goalkeeper Profile

Build a comprehensive goalkeeper profile.

Tasks: a) Create a GoalkeeperProfile class with all major metrics b) Populate the profile for a specific goalkeeper c) Generate radar chart visualization d) Classify goalkeeper style

Expected Output: Complete profile with visualization

Exercise 26: Multi-Goalkeeper Comparison

Compare multiple goalkeepers from a tournament.

Tasks: a) Build profiles for 5+ goalkeepers from the World Cup b) Rank by each major metric category c) Create comparison visualizations d) Identify the "best" overall performer with justification

Expected Output: Multi-goalkeeper comparison report

Exercise 27: Goalkeeper Recruitment Analysis

Apply analysis to a recruitment scenario.

Tasks: a) Define requirements for a "sweeper-keeper" role b) Create scoring criteria for each requirement c) Evaluate 3 goalkeeper candidates d) Make a recommendation with supporting analysis

Expected Output: Recruitment analysis report

Exercise 28: Match Report Generation

Create an automated match report for goalkeeper performance.

Tasks: a) Build a function that generates a text summary of goalkeeper performance b) Include key statistics with context c) Highlight notable saves or errors d) Generate the report for a specific match

Expected Output: Automated match report

Exercise 29: Season Evaluation

Conduct a full-season goalkeeper evaluation.

Tasks: a) Load all available matches for a goalkeeper b) Calculate cumulative season statistics c) Track performance evolution throughout the season d) Provide end-of-season evaluation summary

Expected Output: Season evaluation report

Exercise 30: Goalkeeper Analytics Dashboard

Design a goalkeeper analytics dashboard.

Tasks: a) Create a multi-panel figure with key visualizations b) Include shot map, distribution patterns, and radar chart c) Add summary statistics panel d) Make it suitable for presentation to coaching staff

Expected Output: Complete dashboard visualization

Submission Guidelines

Code Requirements

• Well-commented Python code with docstrings
• Functions should be reusable and modular
• Include error handling for missing data
• Handle the uncertainty inherent in goalkeeper data

Analysis Requirements

• Acknowledge sample size limitations
• Provide confidence intervals where appropriate
• Compare to relevant benchmarks
• Consider tactical context in interpretation

Visualization Requirements

• Clear, labeled visualizations
• Communicate uncertainty appropriately
• Professional formatting
• Suitable for non-technical audiences where specified

Grading Rubric

Additional Challenges

1. Tracking Data Extension: If tracking data is available, incorporate positioning analysis

2. Video Integration: Select 5 key saves and analyze technique alongside statistics

3. Cross-League Comparison: Compare goalkeeper styles across different leagues

4. Historical Analysis: Track a goalkeeper's development over multiple seasons

5. Novel Metric Development: Propose and implement a new goalkeeper metric