Scouting defenders, and in particular young defenders, is hard. Publicly available data on defensive actions during a match (tackles, interceptions, blocked shots, etc.) do not give you such an easy glimpse into a player’s ability compared to offensive players, who can boast strong pass completion or key pass numbers. A player who makes more defensive actions in a game is not necessarily better than the one who makes fewer (Chris Anderson and David Sally coined this conundrum as the Maldini Principle in The Numbers Game, due to the Italian defender’s tendency to make one tackle every two games on average).
So what information can we use to help with this problem? It is highly likely that the most useful information about defender performance is less easy to track (e.g. good positioning and anticipation), but what can we get from the currently available stuff?
In the interest of scouting young defenders, I’ve collected data from 44 fullbacks and centre-backs under the age of 23 from Europe’s top 5 leagues. These players were selected as they have appeared in 20 or more matches this season (no less than 1000 minutes). All data from Opta, via Squawka.
A useful first step is to categorise the actions a defender performs: actions intended to win possession/defend, and actions intended to keep possession/attack.
Collecting per90 numbers for each of these actions, we can add them together to give a rudimentary ‘Offensive Contribution per 90’ (OC90) and ‘Defensive Contribution per 90’ (DC90) measure for each player. Here are our centre-backs:
And our full-backs:
The importance of possession
One thing we can look at is average possession of a defender’s team. The amount of time a team is without the ball and the number of defensive actions that team performs is probably related- Steven Caulker is likely to make more tackles, clearances, etc, than Jerome Boateng. These possession stats are based on number of passes rather than actual time in possession. Below I’ve plotted OC90 and DC90 against average possession for that defender’s team.
Note: You may notice the X-axis is weird, denoting possession as a figure somewhere between 6 and 8. Because most teams post somewhere between 45-60% average possession, I’ve taken the square-root of each average possession figure for each team (this is known as a square-root transformation, and is useful for count data like ours).
TL;DR: Makes it easier to see differences in our data, possession increases from left to right along X-axis.
There is something of a trend for low-possession-team defenders to make more defensive actions, but its not exactly a clear relationship. David Alaba is the massive outlier on the right- very few defensive actions for a very high possession team. Meanwhile, players like Cardiff’s Stephen Caulker, Sampdoria’s Shkodran Mustafi and Livorno’s Federico Ceccherini contribute more defensively for lower possession teams. Arthur Masuaku of Valenciennes and Omar Elabdellaoui of Eintract Braunschweig are doing little defensively for low possession teams, both in the relegation places.
The relationship between a team’s average possession and these defenders’ offensive contribution is a little clearer- the more possession a team has, the more likely the defence is to contribute to keeping possession and attacking the opponents’ goal. David Alaba is the massive outlier again, completing a large number of passes per game. Ben Davies and Daniel Carvajal (who’s labels are overlapping) do plenty offensively, with Freiburg’s Matthias Ginter and Wolfsburg’s Robin Knoche completing a lot of passes.
Splitting our defenders into centre-backs and full-backs is also important. Full backs are more likely to complete a greater number of offensive actions than centre-backs. Here are the same graphs again, but with centre-backs as circles and full backs as triangles. This sample features 18 young CBs and 26 young FBs-
We can immediately see the centre-backs who have great offensive contributions (mainly lots of passes): Niklas Sule, Matthias Ginter, Robin Knoche, and Aymeric Laporte do a lot with the ball from centre back. Emre Can has also played in midfield this season, so his number may be skewed a little.
Layvin Kurzawa of Monaco, Ricardo Rodriguez of Wolfsburg and Timothee Kolodziejczak do a lot defensively for their teams from full-back, whilst Steeve Yago, Matthias Ginter, and Samuel Umtiti don’t register as many defensive contribtions as other centre backs.
Anyone we like?
Robin Knoche completes a lot of defensive actions, but also completes plenty of passes and has a high attacking contribution. Knoche is first choice in something of a porous Wolfsburg defence. One to watch maybe. Hoffenheim’s Niklas Sule is another who completes a lot of offensive and defensive actions, and features regularly despite being just 18.
He gets a bit lost in these charts, but Ricardo Rodriguez of Wolsburg completes tonnes of key passes, and has 0.23 assists per 90 this season. He is already rated as one of the best left-back prospects in Europe, and has been linked with practically everyone. Nurnberg left-back Marvin Plattenhardt also has good key pass stats. Benjamin Mendy of Marseille is another great attacking full-back, although his low completed passes per 90 figure means he gets lost in the cluster too.
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