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Expected Goals Against (xGA)

Expected Goals Against (xGA) measures the quality of scoring chances faced by a team or goalkeeper. While xG evaluates the probability of scoring for attacking teams, xGA evaluates the probability of conceding goals based on the shots allowed. This metric helps analysts understand:
  • Defensive vulnerability
  • Goalkeeper workload
  • Shot quality conceded
  • Defensive structure effectiveness
The value of xGA for each shot ranges between: 0≤xGA≤10 \leq xGA \leq 1 Where:
  • (0) represents a very low probability shot
  • (1) represents a near-certain goal

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How xGA Is Calculated

xGA is calculated using the same statistical model used for xG, but applied to opponent shots faced. Each shot is evaluated based on contextual features including:
  • Shot distance
  • Shot angle
  • Shot type
  • Body part used
  • Defensive pressure
  • Pass type preceding the shot
  • Game situation
The model estimates the probability that the shot will result in a goal. xGA=P(Goal Conceded∣Shot Features)xGA = P(\text{Goal Conceded} \mid \text{Shot Features})

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Total Expected Goals Against

For a team or goalkeeper, total xGA represents the sum of the expected goal values of all opponent shots faced. Total xGA=∑i=1nxGAi\text{Total xGA} = \sum_{i=1}^{n} xGA_i Where:
  • (xGA_i) represents the expected goal value of each opponent shot
  • (n) represents the number of shots faced

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Goals Prevented

Goals prevented measures how effectively a goalkeeper or defense outperforms the expected goals conceded. Goals Prevented=Total xGA−Goals Conceded\text{Goals Prevented} = \text{Total xGA} - \text{Goals Conceded} Interpretation:
  • Positive value → Goalkeeper prevented goals above expectation
  • Zero → Performance matches expectation
  • Negative value → More goals conceded than expected

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Average xGA Per Shot

Average xGA per shot measures the average shot quality allowed by the defense. Average xGA per Shot=Total xGATotal Attempts Faced\text{Average xGA per Shot} = \frac{\text{Total xGA}}{\text{Total Attempts Faced}} Lower values indicate that the defense limits high-quality scoring opportunities.

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Relationship Between xGA and Defensive Performance

Expected Goals Against is closely related to defensive structure. Total xGA=∑i=1nxGAi\text{Total xGA} = \sum_{i=1}^{n} xGA_i Where each opponent shot contributes to the overall expected goals conceded.

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Tactical Interpretation

xGA helps analysts evaluate:
  • Defensive solidity
  • Quality of chances conceded
  • Goalkeeper performance
  • Defensive organization
Teams with low xGA values typically maintain strong defensive structures that limit high-quality shots.

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Example xGA Scenario

Attacker → Through Ball → Shot Shot Distance: 10 meters
Shot Angle: Central Estimated Probability: xGA=0.35xGA = 0.35 If the goalkeeper saves the shot: Goal Prevented If the shot results in a goal: Goal Conceded

Goalkeeping

Metrics describing goalkeeper saves and shot stopping performance.

Defensive Actions

Statistics describing tackles, interceptions, and defensive interventions.

Expected Goals (xG)

Metric estimating the probability of scoring based on shot quality.

Expected Threat (xT)

Metric evaluating how attacking actions increase scoring probability.