The “expected goals” phrase has gained a great popularity in the world of football statistics. Instead of looking at the “shots on target”, football fans around the world are now interested in the xG values. In this article, we’re going to explain what xG means and how you can use xG stats for football betting.
If you’re a football fan, at some point in your life you’ve probably felt that your club deserved to win a match, yet they still lost. They’ve had more chances, more shots on target, and the opponent was lucky anyway. However, statistics like that can often be misleading and show an inaccurate picture of the game. What about the shots that were taken from a distance? Or the ones that were taken from a difficult angle? Some chances are bigger than others, and you can’t express this with the number of shots. That’s why the xG value was created.
With the xG value, we can see the quality of certain chances, not just the quantity of them. Therefore, you get a better picture on which team dominated the match by having bigger opportunities in front of the goal. In this article, we’re going to write about what xG exactly is. We are also going to show you how to use xG stats for football betting.
What are xG stats and how do they work?
The phrase “xG” stands for Expected Goals. When we look at the xG value of a certain team or player, we’re going to see how many goals they should’ve scored based on the quality of their chances. This may sound complicated, but it’s actually not rocket science, and easier to understand through an example.
Let’s say that there’s a striker, who tries with a shot on the goal. The algorithm looks at the circumstances of this shot: where did it come from, was it from a good angle, was it a 1v1 situation with the keeper. Some algorithms include the position of the defenders as well. Based on these circumstances, the shot gets an xG value. Let’s say that our shot’s xG was 0.2. This means that out of 10 situations like that, usually about 2 attempt ends up as a goal.
To give you a better, existing example, look at Danny Welbeck’s shot at the end of the video. This was apparently the worst miss from Premier League’s last season.
The xG map of the game at understat.com tells you that the xG value of this shot was 0.75. This means that 75% of similar attempts have ended up in the goal. Okay, we argue that it probably should be a bit higher (who else in the world could miss this besides Danny Welbeck?). However, the point is that numbers show this was a huge opportunity and it was basically easier to score than to miss. By the way, Charlie Austin had a similar attempt in the same game (with the xG of 0.82) but he scored ruthlessly.
It’s more than just measuring luck
So are we just somehow measuring luck here? Was Danny Welbeck just unlucky? Despite his failed attempt, Arsenal won the game 3-2, but according to Understat’s xG map, the result should’ve been different. They argue that the total xG value of Arsenal’s attempts in total was 1.59, while Southampton had more quality chances (2.17). What can we tell based on these numbers? Were the Gunners just lucky? Yes and no.
Arguing that Southampton should have won the match because they’ve had better chances could be reasonable. Maybe they were unlucky. However, football is played by humans, who sometimes miss big opportunities, while sometimes they manage to score from out of the blue. This could be both luck and talent, it’s up to you to judge.
Again, xG shows the quality of your chances. Let’s say Harry Kane has ten 1v1 situations with the keeper, and scores nine of them. He was probably a bit unlucky with the 10th one. However, if you’re having 1v1s with the keeper every week, and you miss all of them, that arguably has nothing to with luck. In that case it’s probably a matter of your finishing abilities or composure in front of the goal. Just look at Atletico Madrid in La Liga. Based on their expected points (calculated from their chances and the shots they’ve conceded) they should’ve been in the 5th position this season, but they’re currently second.
It’s not just Atletico Madrid being lucky. It means that their forwards score from seemingly not so dangerous situations, or at least don’t need a lot of chances to score a goal. It also means that their keeper is brilliant, and saves those shots which he’s not expected to save at all. Atletico were expected to concede 9 more goals than they this year, but they’ve had Oblak to come to the rescue. He’s surely one of the best keepers in the world.
Expected assists (xA) helps you judge a player’s ability of creating chances
The xG value was basically created for striker recruitment. However, based on the same mechanism it’s not so hard to create other kinds of interesting data. For instance, there is xA, which stands for expected assists. The thing with assists is that if you give a great pass and your teammate scores from it, that’s great. However, if you manage to create an open goal situation for your teammate and he misses, you get zero assists.
We believe you still deserve credit for that perfect pass, as your job was done. It’s not your fault that you have to play football with Danny Welbeck anyway. In our previous example, Jack Wilshere has set up a great chance, and he deserves his credit. According to the algorithm, 75% of the players score from that situation. That means that Wilshere gets a 0.75 xA here for his almost assist, which was ruined by his teammate.
We were also talking about the “expected goals against” (xGA) value in the case of Atletico Madrid earlier. This value shows us how many chances Atletico players were giving away for their opponents. Theix xGA is about 28 this year, which means that based on the chances their oppositions have had they should’ve conceded 28 goals instead of their 19. That data makes us think about different things:
- Oblak had amazing saves throughout the season
- Their defenders managed to block a lot of shots
- Atletico were lucky as their oppositions missed their chances
We could also mention the Expected points (xPTS) value, which shows us that how many points a team should have based on the quality of their chances and the shots they’ve faced. Based on the xG map of Arsenal – Southampton, the visitors had a better xG rating, they’ve had better chances, and should’ve taken the 3 points.
When we add these expected points, we’re going to see how the league table would look like if certain teams could finish their chances more effectively, or if they weren’t conceding from not so dangerous situations. For instance, this season, Valencia could’ve been in the 3rd place if they were more effective in front of the goal. They have had so much quality chances they should’ve scored at least 15 more goals so far this season.
How to use xG stats for football betting
Let’s be clear here: xG itself doesn’t tell you things about future events. It’s ranking the chances of a team or a player. However, it does help you understand what happened in the past games, and by that, it could be easier to make predictions for the next matches as well. Therefore, it could help us, gamblers, to be more wise when we bet on a team or a player. Let’s take a few examples.
Let’s say we visit Unibet Sportsbook to bet on which teams are going to be relegated from a certain league. We’re going to see that most of the clubs at the bottom of the table were beaten over and over again. However, from now on, we can check whether any of these teams has shown positives in their attacking play. Did they have big chances? Were they unlucky in some occasions? Or maybe they had zero quality chances and their defence was a mess.
If a team keeps trying, has quality chances, it could be worth to go to Unibet Sportsbook and place a bet on them. Even if you bet against the odds or try with a longshot bet at one of the online sportsbook sites in the UK, you can now choose more wisely from the underdogs. But there are other examples as well. Let’s say there’s a forward who scored a lot of goals lately against smaller clubs. Should you bet on whether he’s going to score in a big match? Check his xG! If he’s wasted quality chances beside the ones he scored, he’ll probably not score in a big match as he’s going to have less opportunities on a derby day.
At the end of the day it’s up to you how you use xG stats for football betting. It’s a great tool to compare players and teams, that’s for certain. It could help you make better predictions, and by that you could be more successful when it comes to the gambling part of the game.