27.08.2021 • Author: Maximilian Wensch
After we learned about a metric for measuring offensive performance a few months ago in the blog with the Expected Goals approach, this post is about a metric for the defense: Passes Allowed per Defensive Action, or PPDA for short.
The goal of this metric is to objectively quantify the amount and aggressiveness of high pressing teams. It looks at how many passes the opponent plays on average until the team completes a so-called defensive action. Opta Sports, the sports analytics company responsible for generating the data, defines four events as defensive actions: A successful tackle, the interception of a ball, a failed tackle and a foul. The only limitation in calculating the value is that only opponent passes and defensive actions outside the own third of the field are included. Defensive actions inside the own third are not counted, because there is no pressing in the own third.
The PPDA value can then be calculated using the following simple formula:
The lower the PPDA value of a team, the fewer passes were allowed by the opponent before the team tried to intervene with a defensive action. Teams with a lower PPDA therefore have a more aggressive pressing against the ball. One coach known for aggressive counter-pressing is current Liverpool FC coach Jürgen Klopp. During his time as coach at BVB, the team were known for their outstanding counterpressing. In an interview during his Dortmund days, he referred to counterpressing as the “best playmaker in the world.” And at Liverpool FC, Klopp’s affinity for aggressive pressing is also noticeable. In the last two years, Liverpool FC has had the second-lowest PPDA score both times, with 9.13 (20/21) and 8.01 (19/20). Only Leicester City (19/20) and Leeds United (20/21) had lower scores. In the Bundesliga, Bayern are the measure of all things. In the last 5 seasons, they were in the top 3 of the Bundesliga with the PPDA value. They were only beaten by Bayer Leverkusen in the 19/20 season and BVB and RB Leipzig in the 17/18 season. The most passive football in the last Bundesliga season was played by Union Berlin. With a PPDA value of 15.81, Union Berlin had the highest value of all 18 Bundesliga teams.
It should be noted, however, that the metric does not describe the quality of a team’s pressing, but rather its intensity. The metric thus provides information about how active or passive a team is against the ball.
However, if you compare the correlation between the average PPDA value and the points scored in a season, you can see a tendency.
The figure shows the points scored on the x-axis compared to the PPDA values on the y-axis. All teams of the European top 5 leagues from the past season are shown. The trend line shows that the PPDA value decreases as the number of points scored increases. The result is not exactly surprising. Teams that played a successful season and scored a lot of points tended to play a more aggressive pressing against the ball.
If you compare the values of the top 5 leagues among each other, you get the following average values of the past season:
The Spanish LaLiga stands out with an average PPDA value of just 10.3. This is not particularly surprising, as the Spanish LaLiga is known for its high intensity in pressing. This was also evident at the European Championship this summer, among other things. The Spanish national team had by far the highest pressing intensity at this year’s European Championship, with a PPDA value of 8.1.
If you watched the Germany game against Hungary and the other games in this group, the following should not come as a big surprise: Hungary had by far the highest PPDA value at the European Championship with 25.9. Against Germany, the Hungarians had just 30% possession. Nevertheless, as most of you will remember, it was not enough for a German victory…
This game shows that the PPDA value does not allow direct conclusions about the success of a team, but the value gives information about the playing culture of a club or a league. This can play a role in the transfer search, for example. A striker who presses high and often will be more effective in a league or a club with a lower average PPDA.
Like the Expected Goals approach, the PPDA approach provides an objective metric as a basis for comparison in soccer. Especially in tactical preparation, the PPDA value of the opponent can be used to get an objective metric about the pressing of the opponent. What is most interesting is how these metrics influence the scouting behavior of clubs: Traditional live scouting is now increasingly supported by so-called data scouting.
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A brief addendum: As some of you may already have noticed, the Portuguese Primeira Liga has replaced the French Ligue 1 in the top 5 rankings of European leagues. In this article, we refer to data and values from the previous season, so we still include Ligue 1 among the top 5 leagues here.