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.

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.

Expected assists (xA) explained

Sequences and possesions

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.

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.

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