Does a higher xG mean a team should win? The limits of expected goals

What does xG measure?

Expected Goals, or xG, is a value estimated by a model for the probability that a shot will result in a goal. It can use factors such as the shooting location, angle to the goal, and body part, and the factors included may differ from model to model. Therefore, if two websites have different xG for the same match, you should not immediately conclude that one is wrong.

As an example, consider a shot with an xG of 0.20. This does not mean that the shot has already scored one-fifth of a goal. The model estimates the probability of scoring in similar situations, and the actual result of a real shot is still either a goal or no goal. This example is not from an actual match.

The match situation hidden by the total

If you only look at the post-match xG, you cannot know when the chances occurred. The leading team may sit back and defend later, while the trailing team may push forward more aggressively. Only by also looking at red cards, substitutions, and penalties can you better discuss why chances arose.

Even if the totals are the same, the pattern of chances can differ. One very good chance and many difficult shots can lead to the same total. Moreover, a dangerous cross that did not result in a shot or a failed final pass cannot be fully captured by shot-based xG.

How to write the analysis

Instead of writing that a team should have won because they had a higher xG, it is more accurate to describe where the shots were created and during which periods of the match they were more dangerous. If you can separate the result from the performance assessment, you can acknowledge the winning team's finishing ability while also discussing the losing team's chance creation.

Comparing many matches rather than a single match, using data from the same provider, is more appropriate. Even then, you cannot ignore the strength of the opponent, minutes played, and changes in the team. Use xG as a tool that points you to where to look. Do not use it as a final verdict that replaces what actually happened on the pitch.

Putting it into practice

There are also tables that separate xG including penalties and xG excluding penalties. If you mix these two numbers, you may misinterpret the team's chance creation outside penalties. Although winning a penalty is an important event in a match, if you want to discuss the overall chance creation, it is more useful to show that chance separately.

Also be mindful of when the data was collected. The number shown during the live match may differ from the number reviewed after the match. If you use a number seen at a certain time in your match analysis, state that time. If an updated value differs, do not immediately assume another source was wrong. Check the provider, the last update time, and what each figure includes.

For practice, list the shots of a match by time and mark the minutes when goals were scored. This separates chances created before taking the lead from those created afterwards. This exercise helps you understand xG not as a replacement for the result but as information you can use to explain the decisions of both teams.