There are echoes here of the Moneyball technique popularised by the Oakland Athletics in baseball (which is referenced several times) and Tippett draws a connection between it and xG via their facility to refine gauging a player’s ability to one number. The weaknesses of xG Likewise, a one versus one from the edge of the box would be worth the same value, even if there were 6 defenders between the striker and the goal. I’m not particularly surprised that the wider football community has taken an interest in xG. Betting syndicates and professional football clubs have been using it for a few years now – it’s by far the most powerful means of analysing football. There was always going to be interest in a smarter approach to the sport. Has the surge in popularity coincided with Match of the Day and Sky Sports using xG, or do you think there’s something else driving the interest?

Fans have finally begun to pay an increasing amount of attention to Expected Goals stats. Slowly but surely, the media have taken notice of this increase in interest. Football supporters are insatiable consumers of facts. In a sport where knowledge is power, Expected Goals is slowly emerging as the most authoritative form of data. In later sections, we will see how the media have entered the early stages of the xG revolution, what problems they have faced in incorporating it into their broadcasts and where the future may lie for supporter interaction. I am confident that, in a few years’ time, it will be impossible to read a match report without finding a reference to the Expected Goals scoreline from the game.Much of his manifesto feels jarring at first but it is hard to disagree how, far too often, ‘in football, the result dictates the narrative.’ We as “fanalysts” are often consumed by fandom over analysis. So someone striking the ball into an empty net having rounded the keeper from 10 yards out, would be worth the same as if there keeper were present for a one versus one chance. The parts about gambling and how to make money were the least interesting as that isn't why I watch football. It seems like only the rich syndicates will ever make.money from that.

The score granted to each shot is based upon analysing thousands of similar shots across within a massive database and assesses everything from distance and angle, to strong/weak foot, to whether the assist was a high-speed cross or a simple pass.These two books' contents could be summed in one article - even the same article. Considering the amount of blogs covering this, a well-written introdoctury blog article on Expected Goals would probably give you more than these two books combined. At the end of any given match, the Shot Probabilities from either side are added up to reveal the Expected Goals scoreline from a match. For example, suppose that Arsenal play against Manchester City. The London side have six shots over the course of the match, but they are all long shots from distance with a Shot Probability value of 0.1(xG). The Gunners will have amassed a total Expected Goals score of 0.6(xG). Over the course of the same match, Man City only have two shots at goal, but they are both from close range. Suppose that one shot is worth 0.3(xG) and the other is worth 0.4(xG). Man City’s Expected Goals score over the course of the ninety minutes is 0.7(xG). Thus, the xG scoreline from the match would be Arsenal 0.6(xG) – 0.7(xG) Man City. The scoreline would reflect the fact that Manchester City performed narrowly better than their London counterparts. Expected Goals data is collected by several different data companies, football clubs and betting firms. The main provider of xG stats to media companies is Opta Sports, who claim to collect the most complete dataset for the Premier League, English Football League, Scottish Professional Football League and many other divisions across the globe. Opta’s data experts have analysed over 300,000 shots to calculate the likelihood of an attempt being scored from a specific position on the pitch during a particular phase of play.

It’s certainly helped that people have seen the metric on mainstream broadcasts. Sky Sports, in particular, are increasingly using xG as a form of insight on shows such as Monday Night football.

As Tippett explains: "Brentford pride themselves on their set-piece execution and have gained a reputation over the last two seasons as one of the best teams in the world when it comes to dead-ball situations. These can include which players are over-performing, how adept they are at getting into the right positions and who is benefiting from (or being hindered by) the quality of their teammates. I was coming from the author's previous book on the subject, The Football Code, which was a disappointment. I found it too general, too simplistic, way too repetetive. Thus, my hope was that this book would offer a deeper look at Expected Goals, its applications and foundations. Yet, again, I was disappointed. Playmaker sought insider knowledge on this alluring subject, and spoke with X account xG Philosophy to dig deeper into Brentford’s numbers. Besides the numerous typos (quite unacceptable) in the book while working with numbers, it also fails to incorporate some well-known phenomena which could make the book a bit more insightful. For example, it mentions the importance of shooting from stronger/weaker foot several times, but fails to mention a single time that two-footed players (somewhat unsurprisingly) tend to have a better chance outperforming their xG (Heung-min Son, Mason Greenwood).

Some say that xG models aren’t built to be used for single events and therefore xG isn’t always a good statistic to reference for single goals or even single matches, but rather it’s better used over a longer period. What’s your take on that? I use a version of this approach in my own coaching. I always want to help my players find the best possible spaces in which to create the most dangerous possible chances. From that perspective, this book and xG approach is helpful. The noticeable absence of a smart, analytical and scientific voice in the mainstream football media reflects onto he fans who follow such broadcasting. Stupidity breeds stupidity.”I would have loved to heard more about defense and goalkeepers and how to measure their performance in terms of xG. Also, a bit more about how strikers such as Michu and Benteke were briefly overvalued due to one good season. This is mentioned once but not really explored any further. No person who understands the metric is going to argue that it doesn’t give insight into the ability of teams and players. The media are less likely to adopt it, because they are less likely to care about what is right and wrong. This fallacy is called the “bad map is better than no map at all” fallacy. This is a fallacy because logically, you have a better chance of finding the correct way without a map, than with a bad map. A simple thought experiment we philosophers like so much, will demonstrate this. Tippet explains how XG is calculated and why this statistic is important in analysing football results, teams and players.