The modern analytics movement in world football has defined three main metrics to measure defenders: clearances, blocks and interceptions.
Tackles are utilized as well but are less specific to a defensive player.
While the aforementioned categories alone do not tell the entire story of a given player’s effectiveness, they do help define different types of defenders.
A defender like Sporting Kansas City’s Aurelien Collin, for instance, can be explained by looking at his defensive statistics.
Collin is a bruising center back. He is physical, aggressive and consistently throws his body in harm's ways for the sake of SKC. As a result, the Frenchman averages the second most clearances per match (9.9) of any player in Major League Soccer.
He embodies the type of challenge-first defender that will seek out contact and attempt to make life difficult for his mark.
To have a high number of clearances requires good positioning but it is more a result of fearlessness and emergency defending.
Conversely, interceptions are useful in determining how a footballer reads and anticipates the game. Cutting off a passing lane and intercepting a pass helps start an attack quickly. It is far cleaner than a tackle or clearance in terms of recovering possession. It also is less likely to lead to a committed foul.
Defenders with numerous interceptions per match cover tons of ground and are more likely to be intelligent in how they attempt to win the ball back.
The third statistic, blocks, requires a combination of fine positioning and a willingness to sacrifice for the sake of a team. Defenders who consistently block shots provide a duel service—they frustrate attackers and give their goalkeepers much needed respite.
It is an underrated statistic because of how preventative blocking a shot can be.
Tackles offer an insight into a team’s tactics.
To be a player who attempts to tackle frequently is one who consistently involves his or herself in the action of a match. It suggests that perhaps a team’s strategy is to high press to try and win the ball back at all costs.
Defenders and teams that do not tackle too frequently could prefer to sit back and absorb pressure.
There is still much work to be done in regards to statistics in world football and defenders.
That said, though, the metrics discussed above are a useful method for any manager desiring to numerically judge a defenders’ styles and tendencies.
Data gathered from WhoScored?