Expected goals (or xG for short) put simply is the probability of a goal determined by a range of variables such as shot distance, angle, body part and defensive pressure. xG has been around for some time now and is beginning to get some traction in the mainstream sports media. The purpose of this article is to use xG as a probability in binomial distribution models, what we can learn from this. Part two will use hypothesis testing to evaluate the xG value for penalties of 0.78.
20 August 2017. It’s Tottenham Hotspur versus Chelsea at the Wembley. Chelsea center-back David Luiz wins a foul close to the Tottenham penalty area around the 23rd minute, and wing-back Marcos Alonso steps up to take the free-kick. He fires it into the top-right corner of the net, and it’s 1-0 to Chelsea. In the 82nd minute, however, Chelsea substitute Michy Batshuayi heads the ball into his own goal and makes it 1-1.
Per 90 minute numbers don’t tell us everything about players.
While per 90s help compare players who’ve played different amounts of minutes, not all players get the same amount of opportunities on the ball. Players who play in bad teams, or even players who play in teams that keep less possession and attack directly, won’t get the ball as much as players in teams in the same league as Barcelona or Bayern Munich.
By Matt Allen (@mattallen001)
February is upon us and we say good bye to the January transfer market. Clubs from Europe’s top 5 leagues made a total of 533 deals at a cost of £802.8m. These figures don’t include other big spending leagues such as the championship and the Bundesliga 2 which also spend a considerable amount of money. With such high amounts of money flowing around the world, I ask the question: is it an efficient market?
By Raven Beale (@sbourgenforcer)
The Future of Football Analytics
Currently, the biggest issue with football analytics is the lack of positional data for off-ball players. Most of the analytics is done using event based data, in which every pass, tackle and shot is logged. However, event data only contains the ball’s location. This means we as analysts are left guessing on a huge amount of our work. How do we evaluate how difficult as pass is without knowing where the players are on the pitch? How can we quantify the intricacies of good defending against bad defending?
SD Eibar, the smallest club in La Liga which consistently punches above its weight, are currently sitting pretty at 8th in the Spanish La Liga table. The club from a town of 27,000 people in the Basque country, which play at the little Ipurua Stadium, have been putting on some dazzling displays this season under the Basque manager José Luis Mendilibar.
When Barcelona’s 29-year-old midfielder Paulinho scores more goals in the league than a 5-time Ballon d’Or winner, you know there’s something weird going on. Cristiano Ronaldo has only scored 0.4 non-penalty goals per 90 minutes (NPG90) this season. Not ideal for someone who’s famous for wrecking goalscoring records every year.