xG xPlained!

Explaining xG or Expected Goals — A technical term which has crept into the lingua franca of football community

What is xG

Very simply, xG (or expected goals) is the probability that a shot will result in a goal based on the characteristics of that shot and the events leading up to it.

  • Location of shooter: How far was it from the goal and at what angle on the pitch?
  • Body part: Was it a header or off the shooter’s foot?
  • Assist Type: Was it from a through ball, cross, set piece, etc?
  • Type of attack: Was it from an established possession? Was it off a rebound? Did the defense have time to get in position? Did it follow a dribble?
  • Position of defenders/Goal keeper : Was the goalkeeper in position? Was it an open goal or were there a number of defenders between the shooter and the goal? Was the shooter being pressured? Was it a 1v1 situation with the keeper?

How xG is used

xG has many uses. Some examples are:

  • Comparing xG to actual goals scored can indicate a player’s shooting ability or luck. A player who consistently scores more goals than their total xG probably has an above average shooting/finishing ability.
  • A team’s xG difference (xG minus xG allowed) can indicate how a team should be performing. A negative goal difference but a positive xG difference might indicate a team has experienced poor luck or has below average finishing ability.
  • xG can be used to assess a team’s abilities in various situations, such as open play, from a free kick, corner kick, etc. For example, a team that has allowed more goals from free kicks than their xGA from free kicks is probably below average at defending these set pieces.
  • A team’s xGA (xG allowed) can indicate a team’s ability to prevent scoring chances. A team that limits their opponent’s shots and more importantly, limits their ability to take high probability shots will have a lower xGA.

xG explained using xG map

Limitations of xG model

xG model does not take into account the skills of the player who takes the shot.

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