Introduction to Expected Goals (xG)

Understanding Expected Goals (xG)

Expected Goals (xG) has revolutionized soccer analytics by quantifying the quality of scoring chances. This metric assigns a probability value between 0 and 1 to every shot based on historical data.

What is xG?

Expected Goals measures the likelihood of a shot resulting in a goal based on several factors:

• Shot location: Distance and angle to goal
• Body part: Foot, head, or other
• Shot type: Open play, set piece, counter-attack
• Assist type: Through ball, cross, cutback, etc.
• Pattern of play: Build-up preceding the shot

How xG is Calculated

xG models use historical shot data to determine probabilities:

1. Collect thousands of historical shots with known outcomes
2. Categorize shots by their characteristics
3. Calculate the conversion rate for each category
4. Apply machine learning for more sophisticated models

Interpreting xG Values

• xG = 0.01: 1% chance of scoring (long-range shot)
• xG = 0.10: 10% chance (difficult angle or distance)
• xG = 0.38: 38% chance (good opportunity)
• xG = 0.75: 75% chance (excellent chance)
• xG = 0.97: 97% chance (tap-in or penalty)

Using xG for Analysis

xG enables various analytical applications:

• Team Performance: Compare xG to actual goals scored
• Player Finishing: Goals vs xG shows finishing ability
• Shot Quality: Average xG per shot indicates chance quality
• Luck vs Skill: Sustained over/underperformance of xG