Advanced metrics

Expected goals (xG)

Expected goals (xG) measures the quality of a shot based on several variables such as assist type, shot angle and distance from goal, whether it was a headed shot and whether it was defined as a big chance.

Adding up a player or team’s expected goals can give us an indication of how many goals a player or team should have scored on average, given the shots they have taken.

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Expected goals (xG) explained

Expected assists (xA)

Expected assists (xA) measures the likelihood that a given pass will become a goal assist. It considers several factors including the type of pass, pass end-point and length of pass.

Adding up a player or team's expected assists gives us an indication of how many assists a player of team should have had based on their build up and attacking play.

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Expected assists (xA) explained

Sequences and possessions

Sequences are defined as passages of play which belong to one team and are ended by defensive actions, stoppages in play or a shot. 

Possessions are defined as one or more sequences in a row belonging to the same team. A series of passes leading to a shot which is saved and results in a corner kick would comprise one possession since the same team retains control, but for more than one sequence, since the ball has gone out of play. A possession is ended by the opposition gaining control of the ball.

Opta records detailed event data to provide a snapshot of the action at any moment during a match. By combining consecutive events into sequences we’re able to gain more insight into a team’s playing style and an individual player’s contribution.

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Sequence data from Costa's goal against Southampton during the 16/17 Premier League season

Defensive coverage

Defensive Coverage measures the area of defensive responsibility implied by a player’s defensive actions during a match. The corresponding output consists of a series of coordinates which define a polygon of the player’s defensive zone, as well as the area (in metres squared) of that zone.

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Graphic showing Juventus's defensive coverage for the 16/17 Champions League final