It has become de rigueur for manager’s to proclaim at their introductory press conference their intention to play a pro-active style of soccer emphasizing possession and attacking play. This analysis attempts to answer one question definitively—do new managers have an empirical effect on team passing style?—while posing a follow up question for further research—can we use this type of data to “type” managers and give better insight for owners and presidents as they undertake manager searches?
Passes Per Possession
There are many ways to evaluate a team’s passing style, but we have chosen to use passes per possession for a couple reasons: it is simple to calculate (team total passes / team total losses of possession) and it is fairly persistent year over year for our sample (see below) so it will theoretically be easier to find manager change effects.
A higher number of passes per possession indicates a team is more deliberate and possession-oriented in their approach and a lower number indicates a more direct approach when in possession. To give some context, here are the highest and lowest rated three teams for one year from our sample (EPL, La Liga, Bundesliga).
You might notice that the top teams are generally considered among the better teams in Europe while the bottom 3 are not exactly challenging for a Champions League title. While we would caution to call a high # of passes per possession a “good” statistic, it does have some correlation with success—as measured by goal differential.
Manager Change and Passes Per Possession
The sample we are using for this analysis are the 2011-2014 seasons in the EPL, La Liga, and Bundesliga. Since we are using only full season data we excluded any clubs that experienced mid-season manager changes. We only kept teams that either had the manager for a full two years or teams that changed managers in the off-season. In total, our sample included 57 seasons where there was no manager change and 26 where there was an off-season manager change. On average, teams that had a manager change showed a 0.40 absolute change in # of passes per possession and those with no manager change had a 0.26 absolute change in # of passes per possession. We ran a t-test and demonstrated that this difference is significant at a 97% level. We therefore conclude that new managers do have a significant empirical effect on a team’s passing style (as measured by passes per possession).
Although we just tested manager change effects on one specific metric, the fact that it yielded a significant result is an indicator that other metrics may also be tested (team attacking style, other passing style metrics, defensive metrics). Over enough seasons and with a large enough sample size we may even be able to start “typing” managers by their playing style in a deeper quantitative way whereas right now most manager evaluations are of a qualitative nature. For example, Pep Guardiola is generally seen as a coach whose teams favor possession and embody the “tiki-taka” passing style. This intuition is borne out in the data we looked at as both his move from Barcelona and to Bayern Munich saw a corresponding decrease/increase in passes per possession.