xA (Expected Assists)
xA, or « expected assists », measures the quality of the passes that lead to a shot: each pass is given the xG value of the shot it sets up, i.e. the probability that it becomes an assist. A player’s total xA estimates how many assists he « should » have provided.
xA fixes a flaw in the traditional assist: it depends entirely on a team-mate's finishing. A playmaker who lays on three clear chances for wasteful strikers ends the match without an assist, even though he did his job. xA credits the quality of the chance created, whether or not the shot goes in.
In its most common version, the xA of a pass equals the xG of the shot that follows it: a cut-back to an unmarked striker six yards out is worth a lot, a cross headed from the edge of the box very little. Some providers use a variant that rates the pass itself (location, type of pass) whether or not a shot follows, so the figures are not always comparable from one source to another.
Over a season, comparing actual assists with xA helps spot a player flattered by his team-mates' finishing (more assists than xA) or, conversely, an unlucky creator. Like xG, xA only becomes meaningful over enough matches, and it ignores moves that never lead to a shot.
Example
A midfielder plays three passes that lead to shots worth 0.35, 0.08 and 0.12 xG: his xA for the match is 0.35 + 0.08 + 0.12 = 0.55. If none of those shots is scored, he finishes with 0 assists despite 0.55 xA.
Frequently asked questions
- What is the difference between xA and assists?
- Assists count the goals actually scored from a pass; xA measures the quality of the chances created, whether or not the team-mate scores.
- How is xA calculated?
- Most commonly, a pass is given the xG of the shot it sets up. A player's xA is the sum of those values over a match or a season.
- What is the difference between xG and xA?
- In the same move, the xG goes to the shooter and the xA to the passer. Added together (xG + xA), they measure a player's attacking contribution.
See also
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