The Celtic shooting trend that could make difference in treble tilt

One fundamental component of performance is shot-taking. You don’t score if you do not shoot, clearly.

Of course, not all shots are equal and expected goals (xG) has allowed us to evaluate the quality of chances to enhance the simpler shot counts we were able to calculate in more innocent times.

Shooting trends

Let’s consider the trends in Celtic shot taking over the seasons I have the data.

Firstly, plotting the average xG per shot and the percentage of shots taken inside the box. Generally, taking shots inside the box will result in higher xG chances.

We can see that, under the current manager, Celtic are taking a much higher proportion of their shots from inside the box and consequently the average quality of those shots (xG per shot) is increasing. Simple, yes?

You may notice that the seasons with the lowest shot quality and the highest proportion of shots from outside the box were the initial Brendan Rodgers seasons.

There has been a trend across football of taking fewer long shots and trying to work the ball into areas where better quality chances will be created. This is one of the implications of clubs utilising data like xG and working that into their team preparation.

Here is an excellent article from The Athletic showing how the proportion of shots in the English Premier League taken from inside the box has steadily increased over time.

Within the heading section, they name check Rodgers as one of the coaches most responsible for their being fewer shots overall but of better quality. Ironic, because Rodgers was the manager when Celtic had the most shots from outside the box in the chart above.

So Celtic are following industry trends by taking more shots inside the box and seeing an uplift in average shot quality. As noted in the referenced article, the overall volume of shots has not increased – and, in many cases, has decreased.

For Celtic, the total volume of shots in data presented here peaked with Ronny Delia in the 2015-16 season at 19.39. This season a more dominant Celtic team is averaging 17.22.

Shot conversion

Has the improvement in average xG per shot and propensity to take shots from more central locations helped raise the shot accuracy and conversion rates?

To answer this let’s track three different metrics:

- Shot accuracy (simply the percentage of shots that hit the target)

- Shot conversion (the percentage of all shots that result in goals)

- Shot conversion from shots on target (the percentage of on-target shots that result in goals)

Here are the trends since the 2016-17 season:

What we see is a commensurate improvement in accuracy and conversion since the Rodgers era with a definite uptick during the Postecoglou reign and a dip in 2020-21.

This season, for the first time, shot conversion from on-target shots is over 40 per cent. An overall conversion rate of 16 per cent is the highest recorded and a huge improvement on the 11 per cent witnessed in Rodgers’s last two seasons.

It might seem obvious that taking better quality shots (higher xG per shot) from better locations (inside the box) would lead to better accuracy and conversion rates.

As noted with regards to trends, as much as teams are taking more care about where and when to shoot so defensive coaches, armed with the same data, know to focus their players on stopping those very same shooting opportunities.

Note how, at this World Cup, many teams are packing the central areas and forcing their opponents out wide. Spain spectacularly failed to penetrate Morocco’s mid-block where resources were marshalled centrally and densely.

So we see one or two percentage point improvements in accuracy and conversion. Over a season, a one percent improvement in shot conversion would result in around 10 extra goals. That could mean a win in a cup tie, turning a few league draws into wins or defeats into draws. That is why those small margins matter.

Shot location

Thanks to StatsBomb we have some lovely shot location maps, so here is this season covering the SPFL Premiership matches only:

We really need a benchmark to allow comparison so here is the same scope of shot map for the horrible 2020-21 season:

These are quite complex to read but the eye perhaps focuses on the sheer quality of blue shapes outside the box. The colder the colour the lower the xG associated with that shot and the warmer the colour the higher the xG associated.

These charts emphasise that Celtic are attempting more shots inside the box and also more central to the goal.

Much less cluttered and included to illustrate the huge jump Celtic experience moving to compete at the Champions League level, here is the shot map for this season’s group stage campaign:

The average xG per shot has plummeted from 0.137 in domestic league football to 0.105 at the rarefied level.

The level of defending and overall organisation and athleticism is simply much higher while, sadly, the limitations of Celtic’s own players are amplified.

But had the Hoops converted their chances to match the overall xG generated (Celtic scored four goals despite an xG of 8.04) it is likely they would have finished third in the section and ensured European football after new year. Fine margins and all that indeed.

Summary

Shot quality is, unsurprisingly, usually a function of many things. The quality of the players, the overall quality of the team, the style of play, managerial instructions and opposition quality all play a part.

Celtic are following the industry trend by taking fewer overall shots but executing from inside the box and from more central locations. This improves average xG per shot and has resulted in increasing shot accuracy and conversion rates.

Defences are wise to this and it becomes harder to work shooting chances into those locations. This is amplified in Europe and Champions League-level defences were able to limit the Hoops to a much greater degree.

Small increases in efficiency can, however, have a big impact on outcomes and so Celtic should continue to stress the margins of their shooting effectiveness.

READ MORE FROM THIS AUTHOR:

• The Celtic Creatives Part 1: The Ball Progressors
• Inside Celtic's finishing problem
• Why Matt O'Riley has come of age in Callum McGregor's absence