Can xG make you money?
October 15, 2024
Among the multitude of soccer statistics, xG (expected goals) is perhaps the most divisive. In this article we will explore what xG is, how it is used, and run a mini experiment to see whether it can be used for profitable betting on the English Premier League.
What is xG?
xG stands for Expected Goals. It is a performance metric that shows the number and quality of produced chances and, when combined with actual goals, can be used to evaluate how well teams and players are scoring these chances.
Each shot/header at goal is assigned a value based on a few factors including the distance/angle between attacker and goal, number of players between the atacker and the goal, and how many players are within 1 metre of the attacker (i.e.defenders pressuring the attacker). The possible values of xG lie between 0 and 1 and is based on a historical database of identical attempts.
Some examples of xG
An example of an xG of 1 might be Neale Cooper’s goal at 1:41 below:
And an example of a goal witn xG of 0 might be Asmir Begovic’s famous goal for Stoke:
How is xG used? And who uses it?
As mentioned, xG is used to measure performance at creating number and quality of chances. It is often used by football analysts to judge how well managers and teams produce creative play, and how well attackers are at converting those chances into goals.
For example, the Spurs coaching staff will consider xG when deciding on a price to pay for a new striker. Perhaps this explains why they only took Timo Werner on loan, given how profligate he tends to be in front of goal.
xG first entered the conscience of the British public in 2017 when the Opta stat featured on the BBC’s Match of the Day. It quickly gained notoriety among casual viewers for its perceived inability to predict results. It was later included as a metric on the popular Football Manager video game, and now has many supporters who avidly watch their xG score. Still, real-life managers who quote high xG scores as a way to defend their poor on-pitch performance are widely mocked.
So what is the truth? And as sports bettors, can we use xG to not just predict results, but actually make a profit?
EPL and xG: the experiment
Let’s run a real-time xG experiment on the English Premier League (EPL). We will use the xG table as it stands on 10/10 to determine many goals they will score in the following round of games, which will take place between 19-21 October.
Let’s start with the xG table on 10/10/24.
| Rank in xG Table | Team | xG Scored | xG Conceded | xG Difference |
|---|---|---|---|---|
| 1 | Man City | 2.13 | 0.96 | 1.17 |
| 2 | Spurs | 1.90 | 1.02 | 0.88 |
| 3 | Arsenal | 1.85 | 1.41 | 0.44 |
| 4 | Liverpool | 1.71 | 1.12 | 0.59 |
| 5 | Bournemouth | 1.64 | 1.51 | 0.13 |
| 6 | Brighton | 1.54 | 1,12 | 0.42 |
| 7 | Chelsea | 1.54 | 1.50 | 0.04 |
| 8 | West Ham | 1.48 | 1.45 | 0.03 |
| 9 | Man Utd | 1.47 | 1.35 | 0.12 |
| 10 | Fulham | 1.47 | 1,34 | 0.13 |
| 11 | Brentford | 1.43 | 1,84 | -0.41 |
| 12 | Nottingham Forest | 1.35 | 1.39 | -0.04 |
| 13 | Crystal Palace | 1.28 | 1.42 | -0.14 |
| 14 | Wolves | 1.27 | 1.68 | -0.41 |
| 15 | Newcastle | 1.26 | 1.70 | -0.44 |
| 16 | Aston Villa | 1.25 | 1.18 | -0.07 |
| 17 | Everton | 1.15 | 1.64 | -0.49 |
| 18 | Southampton | 1.12 | 1.71 | -0.58 |
| 19 | Leicester | 1.00 | 1.91 | -0.91 |
| 20 | Ipswich | 0.96 | 1.59 | -0.63 |
Now let’s take those xG scores and apply them to the next round of EPL fixtures. We won’t go for exact scores (maybe we will next time) but stick to the 1X2 (match winner) market.
Applying xG to predict EPL fixtures
Here’s the fixture list for the weekend of 18-20 October 2024:
| Home | xG | Away | xG | Predicted Result | Odds |
|---|---|---|---|---|---|
| Spurs | 0.88 | West Ham | 0.03 | Spurs win | 1.45 |
| Ipswich | -0.63 | Everton | -0.49 | Everton win | 3.0 |
| Man Utd | 0.12 | Brentford | -0.41 | Man Utd win | 1.73 |
| Fulham | 0.13 | Aston Villa | -0.07 | Fulham win | 2.5 |
| Newcastle | -0.44 | Brighton | 0.42 | Brighton win | 3.9 |
| Southampton | -0.58 | Leicester | -0.91 | Southampton win | 3.25 |
| Bournemouth | 0.13 | Arsenal | 0.44 | Arsenal win | 1.73 |
| Wolves | -0.41 | Man City | 1.17 | Man City win | 1.33 |
| Liverpool | 0.59 | Chelsea | 0.04 | Liverpool win | 1.62 |
| Nottingham Forest | -0.04 | Crystal Palace | -0.14 | Nottingham Forest win | 2.45 |
Results
This round of EPL fixtures actually provided a decent win for xG. £10 invested on every game meant £100 total invested, with £154.80 returned. A 54.8% return in one weekend is pretty incredible. But one swallow does not make summer, so I will try using xG to predict soccer results on a larger sample size, perhaps covering all 5 big European leagues.
Check back soon for more xG research and don’t forget to sign up for Betlookr’s sports betting predictions.
