Over the past years, you’ve probably noticed the xG (Expected Goals) metric gains a lot of mentions in the media. Pundits and other experts constantly point to this data as a way to back up their arguments or confirm whether a team’s results reflect the performance.
But what does the information mean, and how can it aid your future football betting activities?
Let’s take a closer look at football’s latest stat in greater detail now.
What Is xG (Expected Goals)?
The Expected Goals (xG) metric ultimately curates the data relating to a team/player’s performance throughout a game or season before calculating the number of goals a team should have scored.
You may encounter several terms when looking at the realm of Expected Goals. Here are some that you need to understand.
- Expected Goals (xG): This figure shows the number of goals that should be scored by a team based on the quality and quantity of shots. Can also relate to both teams combined.
- Expected Goals per 90 (xG/90): This figure shows the number of goals an individual player should have expected to score in 90 minutes.
- Non-penalty expected goals (npxG): This figure shows the expected number of goals but excludes penalties from the equation.
- Expected goals for (xGf): This figure shows the number of goals a team should score based on the quality and quantity of shots.
- Expected goals against (xGa): This figure shows the number of goals a team should concede. Again this is based on the opposition’s quality and quantity of shots.
- Expected goals assisted (xA): This figure shows an individual player’s expected assist tally based on the quality and quantity of shots laid on by their creativity.
- Expected points (xPts): This figure shows the number of points a team should have won throughout a season. This takes the opposition of each match into account.
The xG figure is presented as a decimal value, which may initially seem confusing. After all, you cannot score 1.35 goals in a match, for example.
However, the figure is calculated using an advanced algorithm that ranks the likelihood of a shot resulting in a goal. A shot with a 50% chance of being scored will be given a 0.5 rating. Therefore, every shot will be ranked between 0 and 1.
All of the shots over the course of a match are added together to give a complete tally for the game.
This hypothetical example should clear things up:
Arsenal plays against West Ham and takes 10 shots during the match.
The algorithm shows that the probability of each shot becoming a goal is as follows;
20% (0.2), 7% (0.07), 3% (0.03%), 85% (0.85), 6% (0.06),
52% (0.52), 11% (0.11), 14% (0.14), 1% (0,01), and 28% (0.28).
When added together, Arsenal’s xG for the match is 2.27.
How Is xG Calculated?
The xG algorithm was put together by Opta, who analysed over 300,000 shots to find the statistical likelihood of shots being scored. When a player takes a shot, a variety of variables are taken into account. This includes the type of assist, distance to goal, angle, and whether it was taken with the foot or head.
Individual players’ abilities are not considered, so this remains an unbiased and objective metric.
Suppose a player statistically has a 60% chance of scoring a specific shot. In that case, it will be reflected in the data – whether it’s Sergio Aguero or Sergio Busquets.
What Does xG Mean For Football Betting Analysis?
Understanding the basic concept of the xG metric is one thing, but appreciating what it means is another altogether. The data can show how a team is performing with regard to the chances they’ve created and conceded.
Since football is a low-scoring sport, this information often provides far greater accuracy regarding whether a team should be getting results.
More importantly, this is far more accurate than the ‘total shots’ tally, as players may take shots from a distance that has next to no chance of going in. This can skew the data while the xG rating stays true to the team’s performance.
While the result of an individual match might not always correlate to the performance, most teams will generally pick up results to reflect the performance stats throughout a season.
For fans and pundits alike, this can be very useful when analysing how well a team is doing.
For punters, though, the data can transform everything.
Using Expected Goals (xG) Metric In Football Betting
The xG stats can be found on various websites, including Opta and Understat.com. As a punter, you should almost certainly use it to your advantage.
Sometimes in football, teams or players start the game slowly. For example, Harry Kane had a reputation for not scoring in August until breaking that duck towards the end of August 2018.
However, the fact that he was taking shots resulting in a high xG/90 rating suggested that he’d always come good – 59 Premier League goals over two seasons underlines that.
Likewise, clubs often struggle to score for a few weeks. If they are creating chances, you can anticipate an upturn in fortunes at some stage.
Conversely, a team at the bottom of the table struggling on the xG ratings could continue to be in for a tough time throughout the campaign.
Bookmakers usually set the odds and lines in correlation to recent results, which may only sometimes tell the whole story.
With the xG rating metric at your disposal, you can work the odds in your favour on many markets:
When you locate the xG stats for a specific league or tournament, you can split the data into home versus away. The following stats were available after the first international break of 2018/19.
Huddersfield Town xG/90 at home of 0.32 V Crystal Palace xG/90 away 1.05.
So, the statistics suggest that the visitors should sneak a 1-0 win. Of course, we know that football doesn’t always work like that. However, if the hosts were deemed favourites for this game, punters could consider it worth placing a bet on the visitors to win.
Of course, there are always other contributing factors, ranging from team news to extreme circumstances, such as red cards in previous matches.
Still, the xG rating can be used to support your initial thoughts to confirm whether a bet is statistically a good selection.
In addition to the season stats, the xG from the previous head-to-head meetings can be telling.
Total goal markets are another popular option for fans of the xG market. This is because punters can access the expected goals against tally and the expected goals figure. This can provide guidance for bets on the BTTS, Total Match Goals, and Total Team Goal markets.
Teams at the top level tend to revert to the mean throughout the season. Whether this means that their current goals tally will improve or decrease depends on how their performances correlate with recent results.
Either way, you can be quietly confident when making selections based on the xG values.
By no means is the xG information guaranteed that your results will come in. After all, the discrepancy between these figures and actual scorelines shows that anything can happen in football.
Nonetheless, a team that creates a greater number of chances, particularly high-quality opportunities, should score more goals than one that doesn’t.
For that reason, you should always analyse this metric to support your football betting selections. If it’s good enough for the clubs and the media, it’s certainly good enough for you.