xG is a model of “expected goals”. It’s based on the rate of shots on goal. Thanks to them it can be estimated how many goals the team should have scored. This model is very similar to the Expected Value (EV) in poker, so it should be very familiar to those who play poker professionally.
Where did xG come from?
The author of one of the first famous models, Egil Olsen, coached the Norwegian national football team in 1990-1998. Olsen once stated that he did not trust a 1-0 victory if his team made only one hit and the opponent hit ten times. He also won’t be upset with a 0-1 defeat if his team has ten shots on goal while the opponent has only 1.
Football might be unpredictable like that, but the xG model helps to make some sense in betting. Some gambling sites, like 888Sport, with the review from Bookmaker Ratings https://bookmaker-ratings.com/review/888sport-review/, provides many odds options for the players who master how the xG system works.
A simple example: if the team made a shot from a good position, where the probability of scoring a goal is approximately 30%, then the xG system counts this kick as 0.3 goals. Whether the player converted this moment to the goal or blasted the ball to the stands, the number won’t change.
How does xG work?
xG works as follows: each shot in the match gets assigned with a threat ratio. The threat ratio is essentially the probability of scoring a goal.
The system shows us the goals themselves are a very unreliable indicator of team success in a particular match. It helps to identify underappreciated squads that are currently unlucky and if their opponents are too fortunate. Because of this, the small part of the gamblers that do not take into account this stat will underestimate them or, on the contrary, overestimate them.
For example, a team produced 18.4 xG (expected goals) in 10 matches, and its actual result is only eight goals in 10 games. Statistics indicate that the team is very unlucky in attack, and it is worth considering betting on it in the future. Or analyze the odds on total over this team because other gamblers might underestimate them since this squad have scored fewer goals than they should have.
However, the basic statistics that we used to analyze do not reflect the indicator of “luck” in any way. If you see a team with eight goals in ten games in the basic statistics, you will decide that this is a poorly scoring team. Although the team’s problem might be that they have an unlucky streak at the moment, or the squad can’t score their opportunities.
The key factors for calculating xG
Football is a sport with low scores. Goals do not show the real situation on the field often. Therefore, to fully understand football, the xG system comes to our aid, helping to judge the quality of the teams’ better than the positions on the board do. All pro bettors are now making their bets based on xG.
If you use this advanced method, you can be far ahead of the player pool. We will highlight three key factors that affect the probability of a goal:
- Distance to the goal.
- The angle of shot with respect to the goal line.
- The angle of blocking of the shot.
After calculating the probabilities of a goal in all the team’s shots per match, we add these threats to the score and get an alternative score in xG. And with the help of this alternative “xG score”, we can build all kinds of models for predicting the probabilities of outcomes for different events.