Expected Goals Against (xGA) is a key metric in football analytics used to measure the quality of chances a team concedes. Instead of looking only at goals allowed, xGA evaluates how likely each shot faced was to become a goal based on factors such as shot location, body part used, pressure, type of assist, and angle to goal.
This gives a far deeper understanding of a team’s defensive performance than simple goals conceded.
If a team consistently concedes low xGA, they are preventing high-quality chances — regardless of how many goals they actually concede in the short term.
Why xGA Matters
xGA helps answer questions that traditional defending metrics cannot:
- Is a team defending well even if they concede goals?
- Is a team lucky to be conceding so few?
- Is the goalkeeper overperforming or underperforming?
- Is the defensive structure consistent or chaotic?
xGA offers a clearer view of process rather than outcome. A team might concede two goals from extremely unlikely shots, but still have a strong defensive performance according to xGA. Conversely, a team may keep a “clean sheet” but concede multiple big chances — their xGA would expose the defensive problems.
How xGA Is Calculated
xGA uses the same underlying probability model as xG, but applies it to shots faced instead of shots taken.
For each shot the defense allows, a probability value is assigned:
- A tap-in might have an xGA value of 0.70
- A header under pressure might be 0.10
- A shot from 25 meters may be 0.03
You then sum all the probabilities across a match to get the total xGA.
Example:
| Shot | Probability | xGA |
|---|---|---|
| Close-range cut-back | 0.45 | 0.45 |
| Header from cross | 0.12 | 0.12 |
| Long shot | 0.04 | 0.04 |
Total xGA = 0.61
This means the team “should” have conceded around 0.61 goals based on chance quality.
xGA vs Goals Conceded
Comparing xGA with actual goals conceded gives powerful insights:
1. Goals Conceded > xGA → Bad luck or poor goalkeeping
The team is conceding more than the chances justify.
Possible reasons:
- Goalkeeper mistakes
- Deflections
- Exceptional finishing by opponents
2. Goals Conceded < xGA → Overperformance
The goalkeeper or defensive actions are preventing likely goals.
Possible reasons:
- Elite shot-stopping
- Last-second blocks
- Opponents missing big chances
3. Goals Conceded ≈ xGA → Sustainable performance
The defense is performing roughly at the expected level.
What Drives xGA Up or Down?
A team’s xGA is shaped by its defensive system, individual quality, and collective discipline.
Factors that increase xGA
- Poor defensive structure
- Allowing central shots
- Losing defensive duels
- Slow transition defense
- Failed pressing traps
- Large spaces between lines
- Fullbacks caught high
- Low defensive work rate
Factors that reduce xGA
- Compact defensive block
- Good rest-defence structure
- Strong center-backs
- Aggressive counter-pressure
- Forcing opponents wide
- Blocking shooting lanes
- Clean box defending
- Elite goalkeeping positioning
Goalkeepers and xGA: Introducing Post-Shot xG (PSxG)
While xGA evaluates shot quality before the ball is struck, it doesn’t fully isolate the goalkeeper.
That’s where PSxG comes in — it measures how likely the shot was to go in after contact, factoring in shot trajectory, placement, and speed.
Comparing PSxG with goals conceded gives a clearer assessment of:
- Shot-stopping ability
- Reflexes
- Positioning
- Save difficulty
Example:
- PSxG: 12.0
- Goals conceded: 9
→ Goalkeeper is overperforming by -3.0 goals
Combining xGA and PSxG provides one of the clearest pictures of defensive performance.
How Coaches and Analysts Use xGA
Clubs and analysts use xGA to:
1. Evaluate the defensive structure
Is the team consistently allowing good or bad chances?
2. Detect early-season luck
A team might sit high in the table but show unsustainable defensive numbers.
3. Identify tactical weaknesses
Examples:
- Too many cut-backs conceded
- Poorly defended half-spaces
- Vulnerability to crosses
- Breakdowns in rest-defence
4. Recruit defenders and goalkeepers
Players who limit high-quality shots can be measured over large sample sizes.
5. Analyze future opponents
Understanding how and where they concede chances guides match planning.
Common Misunderstandings About xGA
“Low xGA means the team is defending perfectly.”
Not always — they may simply be playing a low-block and absorbing pressure.
“High xGA means the defense is bad.”
Context matters. High-risk, high-pressing systems naturally allow more big chances.
“xGA tells you everything about defending.”
It’s powerful, but not complete.
You also need:
- PPDA
- Duel win rates
- Field tilt
- Pressing traps
- Rest-defence shape
- Turnovers conceded
Conclusion: Why xGA Matters More Than Ever
xGA has become one of the most valuable defensive metrics in modern football because it evaluates not just goals — but the quality of defending actions that led to those goals.
It exposes weaknesses in defensive structure, identifies overperforming or underperforming goalkeepers, and helps analysts judge whether a team’s defensive form is sustainable.
While no single metric can capture the full complexity of defending, xGA provides one of the clearest windows into a team’s ability to prevent high-quality chances — making it essential for coaches, scouts, and analysts at every level.