Seth Dobson gives a Statistical Analysis of Ronny Deila’s First Eight Matches.
When a team struggles early in a league season, it is common for supporters and journalists to question the performance of the manager, as well as the players. When that team is Celtic FC, the criticism can be especially sharp since they are expected to win every game.
The Scottish Champions are currently sitting sixth in the SPFL Premiership, with 14 points after eight games, six points behind surprise table toppers Hamilton Academicals. Indeed, it was a historic 1-0 loss to Hamilton at Celtic Park that set off the most recent round of criticism of new manager Ronny Deila.
In this post, I take a closer look at the Norwegian’s first eight league matches in charge from a statistical point of view.
The premise of my analysis is that a manager should be held accountable for what he can control. Managers do not control who wins or how many goals are scored. The best we can expect from a football manager is that his team is mentally and physically prepared to create chances, and to limit the opposing team’s ability to do the same.
Creating chances means taking shots, and the two best indicators of shot dominance in football are Total Shots Ratio (TSR) and Shots on Target Ratio (SoTR), which are calculated as follows.
- TSR = shots for/(shots for + shots against)
- SoTR = shots on target for/(shots on target for + shots on target against)
The table below summarizes shot statistics for Celtic over the first 8 league matches by season going back to 2000.
Here is how Ronny’s Bhoys rank compared with the previous 14 seasons at Celtic.
Shots for: 1st
Shots against: 12th
Shots on target for: 11th
Shots on target against: 4th
Percentage of shots on target for: 14th
Percentage of shots on target against: 2nd
Based on the two most important measures of shot dominance, TSR and SoTR, Deila is having a tremendous season so far. If we just focus on high-quality chances, i.e., SoTR, Deila is having a better start to his stint at Celtic than Martin O’Neill, Gordon Strachan, or Neil Lennon.
So if we adhere to the premise that the manager’s job is to prepare his team to create chances and limit the chances of the opposition, then objectively Deila is doing an excellent job so far.
This leaves the question of why Celtic is sitting sixth in the table. The answer is simple; football is not chess. It’s more like poker. In the long term, skill determines success. But in the short term, luck matters.
Ronny’s Bhoys have been relatively unlucky so far (as I will demonstrate in a future post on PDO). But if they keep creating chances and limiting opposing team’s chances, then they will likely run away with the league, as expected.