For those coming to this article to discover who is the "best" Premier League centre-back statistically, you are going to be disappointed.
The truth is, evaluating any defender based on the data will rarely show one is better than another, but will instead give you an indication of a player's—or team's—style.
We could compare players in high-pressing sides with those in low-pressing ones; we could contrast ball-playing defenders with those who have a more no-nonsense approach; we could even identify centre-back partnerships by cat or dog-like behaviours.
On this occasion, we ask: What does the data tell us about active and passive centre-backs in the league?
A quick refresher before we start
Reporting a player’s volume of defensive actions (e.g., tackles, blocks, interceptions) per 90 minutes is a near-useless method of appraising their off-ball performance.
Why? Well, by definition, a player can only perform a defensive action when their team doesn’t have the ball. If a team has fewer possessions, their players naturally have more opportunities to defend.
To assess a player’s tendency to take a certain action, we can adjust defensive statistics by counting the number of times they perform it for every 1,000 opponent touches. This is not a perfect measure, though, and there has been some fantastic in-depth discussion on the topic within the football analytics sphere. Team style, game state, and opponent strength can all affect the overall output of a given player.
Nonetheless, for this exercise, we will adjust per 1,000 opponent touches, allowing us to compare players’ styles across a more level playing field.
To begin, which centre-backs would you expect to be high in their volume of active, front-foot defensive actions? Here, we define active defensive actions as "true" tackles (i.e., tackles attempted plus fouls plus challenges lost) and "true" interceptions (i.e., interceptions plus blocked passes). Essentially, these actions are more likely to show players who are looking to "stick a foot in" or step out to engage with their opponent when the ball is on the ground irrespective of their success in those challenges.
Last season in the Premier League, the leader here was Tottenham Hotspur’s Cristian Romero, with 11.5 active defensive actions per 1,000 opponent touches. This is unsurprising, as the Argentina international has developed a reputation as an aggressive, physical defender since joining from Atalanta in Italy last summer.
The above list is interesting from a tactical perspective.
Romero’s metrics are likely to be influenced by his role as the right-side centre-back within Antonio Conte’s back three system. From there, he has a remit to step out vertically towards midfield areas and horizontally to defend wide ones — covering for Spurs’ advanced wing-backs when necessary.
One example of this was against Leicester City last season. As the ball runs loose, Leicester striker Patson Daka is the favourite to retrieve it — but Romero makes up the ground, flying forward...
This role within a back-three system is also likely to explain why we see Cesar Azpilicueta and Trevoh Chalobah at Chelsea, Joel Veltman at Brighton, and Wolves duo Willy Boly and Romain Saiss all rating highly in this measure for last season.
It’s not better or worse defending, just indicative of player and team style.
Meanwhile, Leeds’ style last season showed just how much their defenders were nipping at the heels of their opponents, as they placed four players in the top 10 for volume of front-foot, active defensive actions. This was largely under then-head coach Marcelo Bielsa’s man-marking defensive approach, where his players’ remits were to shadow their direct opponent, before his sacking at the end of February.
Again, this shows how an individual’s output is so dependent on team style.
It is too early to truly assess any numbers from this season, but the signs show just how much of a front-foot defender Kalidou Koulibaly is for new club Chelsea. The long-time Napoli star currently tops the list as the central defender with the most active defensive actions per 1,000 opponent touches among players with 300-plus minutes played.
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