by FMP50 on Jan 25, 2023 7:31 am
Expected goals are a new metric in football statistics that is making the headlines for a couple of years. This metric has made its way in the mainstream media, and is being used and shared now widely by sports journalists . What are expected goals exactly, and how can you use it to our advantage in betting? These are these questions I’ll answer here.
What are expected goals (xG)?
First of all, let’s start with a small definition. Expected goals measure the likelihood of a goal being scored, depending on the action played. This statistic is expressed from 0 (zero chances to score) to 1 (100% of chances to score). To provide this statistics, sports media compare a given scoring chance to thousands of similar occasions in football history. The results are generally provided in terms of the virtual number of goals that should have been scored by a team of a player during the game. For instance, if a team has 1.5 xG (expected goals) during the game, that means the total of their scoring chances adds up to 1.5, therefore that they could have reasonably hoped to score between one and two goals during this match. But of course, that does not tell the whole story! This statistics provides an instant clue based on long term trends, and the reality of the match may differ a lot .
Indeed, it is not uncommon to see a team scoring a goal on their one and only occasion, while their opponents end up losing the game despite having had several huge scoring opportunities. Expected goals are, therefore, a metric that is interesting to use as an analytical tool to understand how a team attacks, rather than a score prediction tool.
xG: expected goals. xGA: expected goals conceded. xGD: difference between expected goals and scored goals
Looking at xG statistics for the current Premier League seasons, one can notice that teams have very different ratios, in line with the playing style they adopt. And that Manchester City dominates the league in terms of scoring chances.
More relevant as a long-term statistic
When used in a short time frame within a single match, several factors limit the relevance of xG. For instance, the match scenario influences the number of chances on both sides because a team that is winning might play more defensively to keep their advantage. Also, the current form of the players that day will result in more or fewer goals scored. Yet, this statistics is more relevant than other metrics such as the number of shots or shots on targets, which can deliver a biased picture of the match if a team keeps on shooting from far without real chances to score.
Especially, the expected goals enable us to understand if a team or a player is scoring more often or less frequently than they should . If a team has an average xG of 3 goals per game, but scores only 1.5 goals on average, that shows that the squad has difficulty converting their chances. In the same line, expected goals to be conceded - xGA - are a telling statistic as well. They provide an understanding of how good are the central defenders and the goalkeepers at getting away from dangerous situations without conceding a goal.
Finally, don’t think that checking expected goals is enough to get a clear picture of the match. If you have a chance, watch it to get a real feeling of what is going on. This is even more important if you are betting live of course!