Opta’s Sam Green<\/a> who, in April 2012, tried to assess the performance of Premier League goalscorers using a model inspired by one used in American sports.<\/p>\nThe team at Opta looked at more than 300,000 shots and a number of variables – including the angle of the shot, assist type, shot location, the proximity of defenders and how far away from the goal the chance was.<\/p>\n
By doing this they are able to assign an xG value, usually as a percentage, to any attempt on goal. The more matches are played, the more accurate the xG model becomes.<\/p>\n
What is Expected Goals?<\/h3>\n
Expected Goals (xG) is a statistic used to describe the number of goals a player or team should have scored when considering the number and type of chances they had.<\/p>\n
It means that supporters can provide concrete evidence to support claims such as “he should have had a hat-trick” or “he should have put that away”.<\/p>\n
Expected goals uses a range of characteristics from scoring chances, with historical data of such types of shots, to predict the likelihood of a player scoring a specific shot.<\/p>\n
It is simply a rough probability of a shot being scored, meaning that a team or player could outperform or underperform their xG value. This simply means that the player, or team, could be scoring chances that most would miss – or they are failing to convert from opportunities that tend to end in a positive result for the attacking side.<\/p>\n
Embed from Getty Images<\/a>