Celtic have become fiendishly difficult to score against in Scotland. Before St Mirren’s penalty in the Scottish Cup and Drey Wright’s speculative long-ranger at St Johnstone, the Premiership champions had kept six clean sheets in a row.

Indeed, domestically, Celtic have conceded 0.79 xG per 90 minutes. This is actually no different to last season but, as they are creating more (average 2.93 xG this season versus 2.77 xG for last) the perception is of a bigger difference between the teams.

Average possession is up from 68 per cent last season to 70 per cent this. That all equates to more control. But what we will explore on this occasion is how Celtic press the opposition and whether they are making it harder for them to play while exerting more control.

Passes per defensive action (PPDA)

An accepted method of assessing pressing effectiveness is a metric called passes per defensive action (PPDA). Essentially, this answers the question ‘how many passes does the opponent complete for every successful challenge or interception or other defensive action?’

This value tells you as much about team style as effectiveness so be warned. Let’s illustrate what is meant by this with the summary numbers from the last five seasons:

Celtic Way:

Since Brendan Rodgers’ final season, the number of passes completed both for and against has been increasing per season and first Neil Lennon then Ange Postecoglou pursued more open, attacking and aggressive football (higher press and more direct passing).

Rodgers’ team was set up to be highly controlled with possession and to press when possession is lost within a tight framework but we need to break out the domestic from the European to get a fuller understanding of what is going on here.

Celtic Way:

Here we see that Celtic’s completed passes is increasing largely due to opponents’ propensity to sit deeper and deeper. St Mirren last weekend were quite rare these days in Scotland in that they pressed Celtic high up the pitch.

Meanwhile, the Hoops’ pressing effectiveness at home is evidenced by a decreasing PPDA for the opponents. The longer Postecoglou works with his squad, the more effective the pressing and counter-pressing becomes.

The contrast when compared to this seasons Champions League is stark:

Celtic Way:

The volume of passes achieved by the opponents this season in Europe has almost doubled over the previous campaigns. This reflects both the standard of the opposition but also the capabilities of the current Celtic squad to scale their pressing effectiveness to that higher level.

Let’s look at more evidence.

Packing

The ability of the opponents to play through Celtic’s defensive lines is measured in packing data.

Celtic Way:

Celtic have had fewer players taken out the game per 90 minutes this season than last as the benefits of Postecoglou’s system start to become second nature to what is now a relatively settled squad.

The most crucial part of team packing data is the number of defenders being taken out the game. This is static on last season and higher than the previous three seasons.

This reflects the risks in Postecoglou’s style. Celtic play a relatively high line and also ask the full-backs to support the attack in aggressive ways. Consequently, they get caught out by counter-attacks more often.

Those risks become amplified in Europe:

Celtic Way:

Against high-calibre opposition, Celtic became easier to play through, exacerbated by their aggressive and high positional play in defence. There was significantly more packing events and more defenders being taken out the game despite increased familiarity with shape and patterns domestically.

This is what we mean by the term ‘scaling’. Does the manner in which Celtic play remain effective when stressed by competing with much better levels of opponents?

Counter-attack chances

Chances with the highest xG tend to be those from counter-attacks or fast breaks. Such chances tend to be against a disorganised and depleted defence; there are simply less defenders and more space between them in such counter-attacking situations.

Here is the overall xG conceded by Celtic from fast breaks per season:

Celtic Way:

Celtic’s low-risk football under Rodgers yielded very few opportunities for the opponents to break against Celtic. The team became much more open under Lennon and in 2020-21 – though in particular the levels of defensive organisation were very low.

The good news is that, under Postecoglou, Celtic are becoming harder to break against and create chances against, at least domestically. The xG per 90 minutes conceded to edging down towards Rodgers levels.

But again, let’s break out the domestic from the European:

Celtic Way:

Scary chart time. The opponents at Champions League level are creating over 1.0 xG per game against Celtic from fast break opportunities. Indeed, the Hoops conceded seven goals from such situations in only six group stage matches. You could say they got what they deserved.

Domestically, Celtic’s average xG conceded from fast breaks is a mere 0.15 per 90 minutes. This is less than in Rodgers’ 2017-18 season.

Summary

Celtic domestically are becoming increasingly hard for opponents to play against.

Such is the cohesion and depth of Postecoglou’s squad, teams are struggling to pass through Celtic’s press and are creating fewer and fewer opportunities from fast break situations that generally yield high xG opportunities.

However, at Champions League level, there is clear evidence that Postecoglou’s system does not yet scale to the demands of that quality of opponent.

Some of this is imponderable – the likes of Real Madrid are just too strong for Celtic to compete against.

Some of it, however, is within Celtic’s gift – does the system require better players who can adapt to the higher level and/or does the system need tweaking to reduce the risks associated with an aggressive attacking style?

This will be an ongoing and vital debate.