What are expected goals?
The Premier League season is off to a flying start, with an incredible 76 goals scored in the opening round of fixtures. But now football fans can see how many goals their team ‘should’ have scored, using Opta’s expected goals statistic (xG). The metric appeared on BBC’s Match of the Day for the first time over the weekend, leaving many fans scratching their heads. Here is everything you need to know about expected goals.
What are expected goals? The expected goals model measures the quality of each chance in a game of football and works out the likelihood of a goal being scored. Opta analysed more than 300,000 shots and a number of different variables to create the expected goals metric. “The metric gives an indication as to how many goals a player or team should have scored on average based on the chances they have had,” Opta explains. The model takes into account a number of factors that might affect a player’s chance of scoring. These include angle, assist type and distance from goal.
OPTA The expected goals stat can be used to find the most efficient players and teams
Premier League teams ranked by goals scored in open play Wed, May 3, 2017 Which Premier League side has scored the most goals in open play this season? Play slideshow Getty Images 1 of 21 Which Premier League side has scored the most goals in open play this season?
How does xG work? Opta assign every shot taken in the Premier League an ‘expected goals value’ (EGV), which is the percentage chance of a shot being tucked away. So, an easy chance that has a 90 per cent chance of resulting in a goal would be given a EGV of 0.90xG. By adding up a team or player’s expected goals, Opta can predict how many goals should have been scored over the course of a season. For example, last season Tottenham’s Harry Kane had an extremely impressive xG.
GETTY Expected goals: Harry Kane had an impressive xG last season