Goals Prevented
Goals prevented subtracts the goals a goalkeeper conceded from the post-shot expected goals he faced, producing the number of goals an average keeper would have conceded that he did not.
What it means
A positive figure means he conceded fewer than expectation from those shots; the unit is goals, which makes the number unusually easy to interpret and unusually easy to over-trust.
Why it matters
It is the best public measure of shot-stopping and the most interpretable, because its unit is the currency of the game.
Where it is used
Goalkeeper assessment over a season, always reported with the shot volume and the average post-shot value faced.
Where it misleads
Season-to-season repeatability is weak, so one strong campaign is weak evidence. Defensive shot profiles and score effects confound it, and most careful treatments exclude penalties.
Key points
- It measures a season well and a goalkeeper poorly.
- Repeatability across seasons is weak.
- Defensive shot profiles and score effects confound it.
- Exclude penalties and say so, or the figure is noisier.
- Report shots faced and post-shot value per shot beside it.
- It says nothing about claiming, sweeping or distribution.
Report the definition, the sample and the date beside the figure, and the figure will survive being quoted by somebody else.