AS TIME seems to pass in slow motion ahead of Sunday’s first instalment of the upcoming Glasgow Derby trilogy, it is worth examining the underlying form of each team.
With the league table having swung dramatically since the conclusion of the winter break, there is no question as to which side has been in better form from a results perspective. However, have underlying performance metrics supported the significant gap in relative results?
We can see that the non-penalty goal difference has reflected the gap in results, but the margin has been far closer when it comes to various metrics relating to chance creation: both for and against.
Generally, Rangers have matched Celtic’s chance creation level per 90 minutes - but they have also conceded a fair amount more. The composition of shots has also been relatively close, with both creating about three clear shots per game, through Rangers have conceded at about half of Celtic’s rate. Shots created off of high pressing has also tilted towards the Light Blues.
The next two graphics show non-penalty xG created and conceded over the eleven-game period, with regressed trend lines added:
Both teams have been improving when it comes to limiting chances by opponents, while Rangers have been improving chance creation to ‘catch up’ to Celtic’s relatively stable level.
However, one of the key variables contributing to the disparity between Rangers’ underlying metrics diverging from results has been the almost three goals conceded in excess of npxG conceded, and Allan McGregor contributing several high-profile mistakes. The following may be a surprising radar, comparing McGregor with Joe Hart over the post-break period:
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Neither keeper has played very well, though Hart’s data is derived from a small sample size due to how few shots he has faced over the period. In fact, as the next graphic shows, he has faced just 1.29 shots per 90 minutes over the 11 games.
McGregor has had four specific errors over the period which resulted in significant xG (high-quality chances) and goals for opponents. Adjusting for those mistakes, the disparity in xG conceded between Celtic and Rangers over the period effectively vanishes. What remains is two sides with extremely similar overall performance metrics.
With two so closely matched opponents, the keeper position may once again be vital in the match. For example, in the February 2 3-0 Celtic victory, Reo Hatate’s vital second goal came on a shot with just 0.29 post-shot xG, while Hart faced just two simple saves versus angled long-range shots from Ryan Kent.
Here are the two over the entire season to date:
Similar to the post-break period, and also reflected in the prior few seasons, McGregor appears to have had a tendency towards positional errors, but also good shot-stopping. Hart has not had a lot to do with such an effective defensive system playing in front of him, but has offered good shot-stopping this season overall as well.
Neither keeper has been very good with their feet, nor added value with claiming crosses or sweeping:
The two keepers have actually offered slightly negative goalkeeper OBV for the season to date, despite both having been good shot-stoppers.
Along with potential issues surrounding the availability of significant players for each team, which keeper is able to limit mistakes, along with the relative effectiveness of each team to try and expose the other’s weaknesses at the position, might be a deciding factor in Sunday’s game.
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