The official Celtic Player of the Year award is next week. Here are key defensive performances from the season so far.
Defensive Action
As I have mentioned before, I have a composite defensive metric called Defensive Action Success Rate which is fully defined in the Glossary.
Secondly, over all defensive actions (not passing) I consider the extent to which Celtic maintained possession as a result of those actions – Possession Won %.
For the season that is, I have included all players with over 900 minutes.

As you would expect, the strikers are at the bottom left. The attacking midfielders are slightly further up and to the right.
Then is gets interesting. The midfielders with more defensive duties are next, with Tierney, who spends most of his time domestically attacking, in that group.
At the top right are the defenders, and Brown. You can see from this the unique job Brown does for the team defensively. None of the other midfielders currently exhibit Brown’s defensive work load. Brown’s defensive numbers are commensurate with a full back.
The central defenders, those that do the most defending, are at the top right. There is very little to chose between the four main players. Benkovic is just into the fabled 80% DASR territory (Van Dijk stands alone in here), whilst Boyata wins back possession with 96% if his defensive actions. Simunovic and Ajer are in close attendance.
Defensive Errors and Defensive 3rd Possession
Next, we look at two metrics, one subjective (defensive errors) and one not (possession lost in own defensive 3rd).
Defensive errors can be poor positioning; giving the ball away in dangerous areas; failing to pick up your attacker; any lack of concentration, judgement or technique leading to the opposition having a chance or the probability of a chance.
Losing possession in your own defensive third means giving the opposition the ball in the 3rd of the pitch Celtic are defending. This is not always a negative – i.e. it includes clearances that do not exit the defensive 3rd.

As you would expect all the attackers are now in the top right with few errors and rarely giving the ball away in their own defensive 3rd.
You may also notice Bain and Gordon give the ball away in their own 3rd about the same rate. Bain has less defensive errors this season, however.
Ignoring the top right corner, it is again noticeable that Brown, despite his heavy defensive duties, has a low error rate.
An outlier is Tierney who is very much a safety-first defender. He has a relatively high final 3rd possession loss rate but a very low error rate for a defender. The two are connected!
Of the core defenders, once again Simunovic, Ajer and Benkovic are tightly aligned. Ajer, being the younger player, is to be commended for performing at the same level as more experienced colleagues. Ajer is keeping pace with the more expensive and more elegant Benkovic. Given many would see Benkovic as a star in the making, and as he is not a Celtic player, Ajer looks a suitable replacement.
Boyata, marginally our most effective defender based on the first chart, is also rather alone in having the 2nd highest error rate, and by far the highest rate of defensive 3rd possession loss.
It should be obvious from both charts how far Hendry lags behind the other four main central defenders.
Summary
Celtic have four very similarly performing central defenders, and Boyata is arguably the most successful in defensive actions. However, he is also the most error prone and gives the ball away in defensive areas the most. Both Ajer and Simunovic are comparable to Benkovic, who looks a class player.
Note the job Brown does in terms of defensive actions. No one in the squad replicates his role.