Expected Goals are a useful metric over the longer term, because any good xG model will see its players regress back to the mean over time. It means that are certain points of a season we can assess a player's goal total, compare it to their xG total, and identify players who are either over or underachieving the model.
EXPECTED GOALS (xG) assesses 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. From there that shot is assigned an xG score and the cumulative total of these scores provides a team's xG for a match.Stats Definition
Players will generally return to their Expected Goals over an extended, and so in this case FC are identifying players who are overperforming their Expected Goals total by four or more - which should help to signify players who are ahead of their numbers this season.
OVERPERFORMING XG: TOP FIVE LEAGUES
Player Goals v xG
|#||Player Name||Team||G||xG||xG Diff|
|3||Joao Pedro GALVAO||Cagliari||16||10.9||-5.1|
Ciro Immobile is a two-time capocannoniere winner so he is well-versed in scoring prolifically but even by his standards his season is exceeding expectations.
Scoring 7/8 penalties already puts him 1.75 ahead of xG, while two goals from improbable positions away at Bologna added a huge additional 1.85 xG. In short, he is over-performing largely because of these incidents and, in the main, his positioning and overall goal-to-xG record on a match-to-match basis is good.
Jadon Sancho, until this break at least, was having a season to remember. His shot accuracy and conversion rate is among the best in Europe despite him not being a striker, he has recorded 14 goals from 44 shots. When Sancho is finding himself in good positions, he is scoring the chances.
Pierre-Emerick Aubameyang has been lethal in and around the penalty spot, which is shown in his amount above his xG, though his number is tied up predominantly in away games at Watford and Norwich, where he struck four goals from just five shots, total.
Jamie Vardy's efficiency for Leicester for this season has been phenomenal and it's no surprise that in the past months as Vardy's goals regressed back to his xG (his over-performance had been much higher than this) so too have Leicester hit an overdue return to average.
In France, Moussa Dembele has filled in the gaps left by Memphis Depay's serious injury and both players have been clinical in their finishing - in Depay's case usually from low-xG positions.
In Germany, Phillip Max's xG difference can be largely explained by his free-kick goals from ludicrous distances - one of which carried an xG of just 0.02. And Sassuolo duo Francesco Caputo and Jeremie Boga - the latter a target for some of Europe's biggest clubs - are both overperforming by four goals or more.
WHAT DO THESE NUMBERS MEAN
These players over time will move back towards their Expected Goals numbers. One of the purposes of the xG model is to show what a player should consistently be scoring. If these numbers remain high season on season, it means a player is excellent at finding himself in good positions to score. If this is maintained over time, good players will continue to score a high number of goals.
Getting into positions to score is often the hardest thing in football.