The Problem Position
With Boyata injured and Simunovic making high profile errors, the Celtic central defence is under scrutiny again. Ajer and Hendry are young in a position where experience is vital, and Compper hasn’t played a minute. Is this Celtic’s problem position?
As always, the Glossary is a great reducer where confusion is concerned.
Statement of Limitations
Firstly I will restate that analysis of defensive performance is a lot harder than attacking play. With expected goals and assists slowly becoming common conversational currency, and with a plethora of data around shots at goal, creativity and goal chances, attacking analysis is prevalent.
Defensive play is as much about what is prevented, what does not happen, as events that do. The avoidance of danger through good positioning and team alignment are not data points within my grasp.
And finally defensive play is as much about the unit as any individual. It is standard to hear managers speak of “defending from the front”. Defending is an 11 man job, with team shape and spatial organisation accounting for many hours on the training ground. That collective data remains elusive to the amateur data analyst other than pointing out examples from videos of games.
But, undeterred, I nevertheless collect a number of defensive based event data points so we will make the best of what we have!
Unsettled Defence
This is my fourth season collecting detailed data, so we can go back to the final Van Dijk days for comparison purposes.
In each season I have only included players appearing in at least 10 matches worth of minutes in that position. Here are the included players with their minutes player at centre back and how many 90 minutes this equates to.
Despite being champions in each of the last four seasons, Celtic are not a particularly parsimonious team as the goals conceded per games averages show.
Always remember the recent high-water mark of Celtic central defensive performance occurred in Lennon’s last season when Forster, Van Dijk and Ambrose (oh yes!) broke the Scottish “minutes without conceding a goal” record in 2013/14. No surprise then that the best overall defensive record in the post Lennon era occurred when Van Dijk was present (in combination with Denayer) in 2014/15, conceding 0.72 goals per game. Van Dijk (equivalent of 57 matches) and Denayer (42) were regulars and formed a consistent partnership throughout Deila’s initial season.
The loss of both Van Dijk and Denayer the following season was, inevitably, hugely disruptive. Five players played the equivalent of 10 matches or more in this position, but none more than Boyata (equivalent of 39) with Ambrose being the next highest on 22. Boyata, Simunovic and Sviatchenko were all new singings to be assimilated. Not surprisingly, the goals per game average shot up to 0.95 despite the opposition, on average, having less shots.
Under Rodgers, the goals against fell slightly to 0.85 per game, despite playing Champions League football (and losing 7-0). There were four players regularly appearing at centre back, and only Simunovic (31) and Sviatchenko (35) completed more than 30 games worth of minutes. Toure was brought in to add experience and short term stability but was largely discarded after a nightmare against Borussia Moenchengladbach. Boyata, the erstwhile Van Dijk replacement, managed the equivalent of 21 matches.
And so into this season, if we add in the Patrick Thistle game, sees Celtic up to 1 goal conceded per game – the worst record since 2009/10 under Mowbray when 57 were conceded in 54 matches. Defence partnership stability remains elusive. Boyata (now injured) leads with the equivalent of 26 matches played, whilst Simunovic (20), Bitton (17) and Ajer (16) have been semi- regular. Celtic have played 44 matches so far this season and only one central defender is over 50% utilised.
Here is the partnership data from the last four seasons:
Since Van Dijk and Denayer appearing together 37 times in 2014/15, there have been few double figures partnerships. The Simunovic / Sviatchenko partnership in 2016/17 was 15 matches together – the next highest.
We will go onto look at individual performances, but it is clear from the above that the lack of a settled partnership has been apparent for 3 seasons. Defending is a lot about communication, understanding and appreciation for each other’s positioning. Constant change of personnel, no matter how talented individually, weakens the overall strength of the defence. Irrespective of individuals, a settled pair would surely be an improvement.
Defensive Action Success Rate (DASR)
DASR is my aggregated metric that is, according to the munificent Glossary:
“The proportion of Successful Challenges as a % of all challenges attempted (Successful Challenges plus Unsuccessful Challenges)”.
By Challenges I take:
Tackles
Aerial Challenges
Intercepts
Blocked Crosses
Shield Outs
Blocked Shots
Unsuccessful Challenges are:
Tackles Lost
Aerial Challenges Lost
Missed Blocked Crosses
Missed Tackles
Fouls Committed
Therefore DASR is useful indicator of competence across a range of basic defensive actions.
Looking across the 4 seasons of data, and including only those that played at least 10 matches at centre back, the cumulative DASR for those performers is:
Using just the eye test I would posit Van Dijk is the gold standard of recent Celtic centre backs. The £75 million defender appeared an adult playing against children on occasions. He leads the four season DASR ratings. As you can see, the margins are small and a current player occupies second spot. Ajer has only 1395 minutes as a Celtic centre back but it is an encouraging start.
There isn’t really a lot to choose between the rest by this criteria but it is concerning four of the current five incumbents occupy the lower positions.
Possession
A good centre back should win back possession and at the same time rarely lose possession, being the last line before the goal.
Again, possession is defined in the glossary. The comparative possession data for the recent centre backs is:
Once again, Van Dijk leads the way with the best ratio between possessions won and lost. He also has the highest average possessions won per 90m at 6.94. Simunovic loses possession at the lowest rate amongst this group at 0.73 per 90m. Bitton stands out as the player losing possession the most, being new to the position.
Toure’s data is interesting – I am wondering whether the lack of possession lost or won is due to his relative low involvement in games which may be to do with (lack of) dynamism and age but also good positioning meaning interventions are less frequent?
Sviathcenko – a noted aggressive defender, is the 2nd highest possession winner. Denayer being in the middle may be an effect of him playing alongside Van Dijk for the vast majority of his appearances and being the defender more likely to drop off rather than engage.
And finally a reminder that Ambrose could be an effective central defender. Speaking of Ambrose…..
Defensive Errors
I subjectively assess this and most errors are to do with giving the ball away in dangerous areas, poor defensive positioning or rash actions leading to chances. For Simunovic watchers, the Partick Thistle cup game is not included in this data.
Very early days for Ajer, but again a promising start from a small data sample.
The Denayer / Van Dijk partnership again was a solid one from an error perspective.
I do wonder what Sviatchenko has done wrong – it may be his footballing skills are not as conducive to Rodgers passing strategy (we’ll come to that).
Simunovic has had a bad time recently but is generally middle order on the error front. Boyata has actually come down from the 0.9s in his early Celtic days. The worst offenders are no surprise albeit Toure’s demise was sudden and brief.
Passing
I don’t have forward passing effectiveness (packing) data beyond this season so cannot yet compare that. But simply looking at complete and incomplete passes tells a tale.
All five current central defenders are present in the top six positions. Whether this is due to a self-fulfilling prophecy or not can be debated (are the leaders the most accurate passers, or are they at the top due to following team strategy orders?). But the current cadre execute significantly more passes, and more accurately than the Deila cadre. There may be a hint here of why Sviatchenko is not favoured with his relatively low passing involvement. Rodgers prefers converted passing central midfielders (Bitton and Ajer) to granite old school enforcers like the Dane.
Small margins again, but the current demand is for 95% + accuracy, not 90-94%.
Conclusion
Van Dijk remains the highest calibre centre back of recent times and none of his successors achieve his standards as yet. Furthermore, his partnership with Denayer delivered the lowest goals against per game ratio of the last four seasons. Not only were they talented players, but they formed a partnership that endured for the vast majority of the season.
Whether by design (switching between 3 and 4 at the back, giving players a chance) or accident (injury) Rodgers has not had a settled centre back pairing in his tenure. This in itself would tend to have a negative impact on team defensive performances.
Of those in the current cadre, Ajer has made a very promising start but we need to remember that he has not played European football in this position for Celtic (late edit: impressive against Zenit!). For the rest, there isn’t much to choose between them in terms of the numbers. Sviatchenko seems to be out of favour as he doesn’t fit the passing style of the manager. Simunovic is still young for a centre back and could improve. Boyata looks solid across the dimensions without looking like reaching the Van Dijk standard. Bitton, I hope, is an occasional stand in. Compper and Hendry are not included in analysis as we have barely seen them.
I think this remains a problem position for Celtic, but a regular pairing of average performers is surely preferable to constant change. Ajer is a beacon of hope.