Where Did xG Come From?
xG, or Expected Goals, was is a methodology by Alan Ryder, who wanted to measure the quality of a shot at goal, but not in Football. No, xG started when Alan stated:
Not all shots on goal are created equal.
He was right, and his research has since inspired other sports and data geeks and gurus to focus on their own models for creating xG (Expected Goals). If xG is the measure of quality for the shot taken by a team, then what factors go into it?
- Assist Type
- Distance from Goal
- Type of Attack
- Shot Angle
- Body Part Used to Shoot
You can see why having Kevin de Bruyne or Trent Alexander-Arnold on your side would increase a teams xG. They create better chances for other players to score. The passes are so good that the chance of the forward scoring is higher. Sergio Aguero is a lucky man.
In the past few years, xG has become a key indicator of how dangerous a side can be, or in some cases how little chances they create. It's a very interesting statistic to study and one that really can help when it comes to betting on football. Some teams might have a high xG per game, but a low number of actual or average goals scored. This kind of trend suggests that the side needs to invest in a better forward, as the chances are clearly there.