What is Expected Goals Against?
The number of quality scoring chances the opposing team created while this player or team was on the ice.
What this tells us
When this player is on the ice, how many dangerous shots did the other team take? xGA weights each shot by how likely it is to go in — a shot from the slot counts more than a shot from the blue line. A lower xGA means the player is preventing the opponent from getting good looks at the net, either through strong defense or by keeping the puck out of dangerous areas.
Limitations
xGA only measures what the opposing team *shot* — it doesn't account for plays that *didn't* result in a shot but were still dangerous (a perfect pass that got blocked, a rebound the goalie smothered). It also doesn't tell you whether the player was in a good defensive position or just got lucky; a defenseman with low xGA might be excellent, or his team might simply be outskating the opposition. That's why we pair it with Corsi Against and other possession metrics to see the full picture.
Formula[show]
xGA = sum of individual shot quality values for all shots taken by the opposing team during player's ice timeHow PuckLab calculates this
PuckLab uses its v2 expected-goals model (56 features, AUC 0.758) to assign a danger value to every shot. Full methodology will be available on /methodology.
Example
A top-pairing defenseman typically has an xGA/60 in the range of 2.0–2.5. A bottom-pairing defender or a forward on a struggling team might be closer to 3.0–3.5.