What is Expected Goals in Soccer?

You may have heard the term expected goals at one point or another when watching or reading about a soccer game. This is a relatively new term and statistic that has only been around for a few years. We’ll explain expected goals in soccer, and what this statistic should tell you. 

Explanation

By definition, expected goals (xG) is a statistical concept used in soccer to measure the quality of scoring chances a team or player has during a match. It helps assess how many goals a team should have scored based on the shots taken by that team, rather than simply counting the actual goals they scored. 

While xG doesn’t affect the scoreline at all, it is used to analyze a team or player’s performance beyond simple goals and assists. Since soccer is such a low scoring game, a statistic like this can tell a more in-depth story about how a game played out, how an individual performed, or how a player/team has been performing over a season. 

How it works

Each shot taken in a match is assigned an xG value, based on historical shot data, to assign the probability of that shot resulting in a goal. The xG value is based on several factors, including:

1. Shot location: Where on the pitch the shot is taken from (closer shots tend to have higher xG values and shots from narrower angles have lower xG values, for example).
2. Shot type: Whether it’s a header, from the foot, a volley, etc… 
3. Assist type: The quality of the pass or cross leading to the shot (a pass in behind the defense leading to a 1 v. 1 with the goalkeeper may have a higher xG value than a cross from wide into a crowded box).
4. Defensive pressure: How much pressure the shooter faces from defenders or goalkeepers. Usually measured by the distance from the nearest defender.
5. Goalkeeper position: The location of the goalkeeper when the shot is taken. A low cross to an open player on the back post with the goalkeeper on the near post will have a higher xG than a regular shot from the same position with the goalkeeper closer to the shooter.
6. Other factors: Such as the assist quality (easy pass on the ground vs. a hard bouncing pass), whether it’s a one-on-one chance, or whether the player is in a favorable position, like unmarked in the box.

Examples

• A penalty kick has an xG of 0.79, meaning there’s a 79% chance of it becoming a goal based on historical data of penalty kick success. 
• A long-range shot from outside the box might have an xG of 0.05, indicating only a 5% chance of resulting in a goal.
• Depending on the angle, speed of play, and defensive pressure, a one vs. one opportunity could typically range anywhere from a 0.4 to a 0.7 xG. 

Why xG is important

1. Better Reflection of Overall Performance: Traditional stats like goals or assists don’t account for the quality of chances. A team might score a few goals but have created very few good chances. Maybe they were fortunate with a lucky shot or bad goalkeeping from the opponent. Conversely, a team might lose despite having high-quality opportunities but failing to score.
2. Predictive Power: xG can help predict future performance. Teams with high xG but low actual goals might be “unlucky” or inefficient, while teams with low xG but high goals might be overperforming or have a great finisher. Their actual goal output could revert closer to their expected goals, or they could isolate and fix a problem relating to finishing their chances. 
3. Assessing Player/Team Quality: xG can help identify whether a player is finishing their chances well or whether a team is creating high-quality opportunities. This can be useful for coaches, analysts, scouts, and even fans.

How teams can use xG

When looking at a team’s total xG for a game or season, you get a sense of how many goals they “deserved” to score, given the quality of chances they created. If a team regularly outperforms their xG, it may indicate they have an exceptional finisher or goalkeeper. If a team underperforms its xG, it may indicate issues with finishing or finishing luck.

Either way, teams can better isolate certain issues to fix on the training ground or with personnel decisions. 

Does it matter for fans?

Probably not for casual fans who want to enjoy a good game and only care if their teams wins or loses.

For the soccer nerds, however, xG can give more insight on the flow or dominance of one team in a match. It can tell you how well they played to an extent (did we create or give up a lot of good chances?). Not that it changes the final score, but it does give you fuel to argue about with your friends or random strangers online.

I like it because it tells me about how key players, mostly attackers, are performing over the course of a season. I know who to blame if we’re struggling, or who to credit if we’re cruising. There are a lot of other stats that you can look into as well, but this is a quick and dirty way to see if your players are performing above or below expectations.

On the flip side, focusing too much on stats and advanced metrics as a fan can detract from the enjoyment of the game. Also, soccer is a game that flows and is not as easily broken down into individual plays like other sports (baseball and football, most notably), so stats usually don’t tell the whole story.

Verdict

While xG doesn’t technically put any points on the board, it can be an effective statistic to better inform fans, coaches, and players. Since xG relies on many subjective factors, there’s always going to be some debate about the xG of any given shot (and even different models will give the same shot different values). It’s not perfect and xG doesn’t directly win you games, but it does tell you a lot more than just the scoreline.