Celtic have scored 23 LESS goals in the SPFL after 32 matches than last season. The title is within view, but what about the entertainment?
In 2016/17, the treble was founded on a dominant SPFL campaign in which 108 goals were scored.
Celtic scored more goals than the quality of the chances they created would suggest. We can measure that through Expected Goals (xG) and Expected Assists (xA).
The Glossary puts it on a plate in the middle of the 6 yard box.
2016/17

What this shows is that from the start of the season, Celtic outperformed their xG. The Green line is above the Orange line all season and by the end of the season the gap is getting wider. The quality of the chances Celtic created (based on where the shot was taken, the game context e.g. a corner, and the part of the body) suggests they should have scored 89.527 goals rather than the 108 finished.
Expected Assists (xA) will almost always be lower than xG as not all shots are created by another player – e.g. a shot following a clearance from a defender. The quality of chances created falls away slightly by the end of the season and suggest, from Celtic passes, 71.103 goals should have been scored.
It was a wonderful season and was it a case of everything touched turning to goals?
2017/18

This season Celtic matched or exceeded their xG up until match 22 – the last game before the winter break, the 0-0 draw against The Rangers. In 2018, since the winter break, their performance against xG has declined with 4 more scoreless matches following. Celtic scored in every league game last season. The Green line is now below the Orange and declining (my data goes up to the 0-0 vs Dundee).
Overall 62 goals have been scored but 69.233 have been expected. Celtic have created 58.022 xA worth of chances.
Summary
This table summarises the significant drop off in chance quality conversion.

Through 32 matches, Celtic have created almost the same xA worth of chances – around 58. Chance creation seems to have been maintained.
But whereas in 16/17 at this stage Celtic had outperformed their xG by over 10 goals, this season they have underperformed by over 7 goals.
There will be many reasons for this and you can explore my earlier articles for the explanations.
In summary the following factors will be prevalent:
Injuries to the major creative talents throughout the season.
Lack of consistency in striker selection.
Specifically, a failure to convert shots outside the box. 14 times last season long range efforts broke the deadlock and opened the game. 24 goals were scored from outside the box, this season it is 9.
Natural regression to the mean in terms of performance against xG – last seasons was exceptional and difficult to maintain.
This article was written with the aid of StrataData, which is property of Stratagem Technologies. StrataData powers the StrataBet Sports Trading Platform, in addition to StrataBet Premium Recommendations.
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