Holiday Power Rankings
How do things look around the midpoint of the European football season?
Most of the continental leagues are going on break while the English Premier League prepares for its holiday fixtures. Here at Expecting Goals, there will be multiple new studies to publish in January, including some updates to the Power Rankings model. To prepare for potential changes, I have added two columns to the tables which note changes from the last published Power Rankings. Today, the new columns simply mark where the team’s performance in recent matches has moved its ratings from the December 5 version of these tables.
You can read the initial newsletter introducing the model for a full description of the method, but broadly it is based on a combination of expected goals created and conceded, actual goals created and conceded, and estimated team value from TransferMarkt, with adjustments for schedule difficulty, home field advantage, and time played with a man advantage or disadvantage.
This post will include the updated Expecting Goals Power Rankings for each of the big five European leagues: the Premier League, the Bundesliga, Serie A, La Liga and Ligue 1. Because the model is based on league football only, the ratings are only scaled relative to the league, they do not project how well two teams from different leagues would fare against one another.
Here’s what the columns in the table mean.
Glossary
Team Performance: This is a measure of how well the team has played in its matches this season, based on statistics that best project future quality, adjusted for red cards and opposition quality. It is expressed in goal difference per match. You can think of this as, how many goals better or worse than the average team has this club played over the season?
Performance +/-: This is the change in the team’s performance rating from the previous published version of the power rankings (in this case December 5).
Attack Performance: This is the attacking component of Team Performance. How many goals better has this club’s attack been, compared to the average team, over the season so far?
Defense Performance: This is the defensive component of Team Performance. How many fewer goals and scoring chances has this club’s defense conceded, compared to the average team, over the season so far? Note that better defensive performances here are negative, in the sense that the team has conceded fewer chances and goals than average.
Schedule Difficulty: This is the opposition quality adjustment, also expressed in goal difference per match. A team with “+0.1” schedule difficulty has played a schedule which is harder than average by a margin of 0.1 goals per match. This measurement takes into account home field advantage and the team ratings estimated quality of opposition. A positive Schedule Difficulty reflects a harder schedule, in the sense that the team’s typical opponent is better than average.
Team Rating: This is the current overall rating for this club, representing how my system will project their future performance. It is based on a weighted average of team performance combining goals and xG, regressed to estimated team value, and for promoted teams past performance is adjusted for league difficulty. Team Rating is scaled to 1.0, with 2.0 being a team that is roughly twice as good as the average team and 0.5 being a team that is roughly half as good as the average team.
Rating +/-: This is the change in the team’s projected rating since the previous published version of the power rankings (in this case December 5).
Attack Rating: In the model itself, it is Attack and Defense Rating which are used to project matches. In the newsletter below I will get into the guts of what makes these up, but the basic components are what I listed under Team Rating. Like Team Rating, Attack Rating is scaled to 1.0, with 2.0 being an attack roughly twice as good as league average, and 0.5 half as good as league average.
Defense Rating: This is the defensive component of team rating. Note that while it is scaled to 1.0, now lower numbers are better. An 0.5 Defense Rating reflects a defense roughly twice as good as league average (that is, conceding half as many goals), and a 2.0 Defense Rating reflects a defense roughly half as good as league average.
Premier League Power Rankings
See the actual Premier League table from fbref.com here.
