Stats review: TSR, SoTR and PDO

During the last week we had a look at some pretty basic stats that are familiar to almost everyone. You can see our analysis here:
Part one – about the offensive performances in the Superliga

Part two – about the defensive performances in the Superliga

In this last stats review for now, we will introduce three stats measures that most people probably have not heard about: TSR, SoTR and PDO. Nevertheless, these measures have gained plenty of attention from football/statistic freaks around Europe lately. Just visit these three links to get an idea:

Counter attack

Bitter and Blue

Bundesliga Fanatic

Let us shortly introduce the measures:

TSR, Total Shots Ratio, is a team’s share of the total shots in their matches. This is defined as:

TSR=Total shots by team/Total shots by team and opponent

SoTR, Shots on Target Ratio, is a team’s share of the total shots on target in their matches. This is defined as:

SoTR=Total shots on target by team/Total shots on target by team and opponent

PDO, is a measure from hockey, that has been applied to football. Our use of it is to evaluate how lucky/unlucky a team has been during the season. PDO is defined as:
PDO=1000x(Saving%+Scoring%).

Okay, with these measures defined we set out to look at the current state of the Superliga! Let us just quote a few lines from the Counter Attack link to underline the relevance of the TSR measure:

Well, Total Shots Ratio is a good predictive metric for points totals and stabilizes over 4-6 games (I feel like I’ve written this sentence about a thousand times now). Teams with a high TSR tend to finish higher up the table over the course of a season. Ta da!

With 15 rounds of Superliga played we should have good data in order to predict who will advance and decline in the table. All excited we start with the TSR table:

 

According to this, FC Copenhagen are by far the strongest. They create most chances and allow the least. The fight for second place is fierce and it will be between Brøndby, FC Midtjylland and AaB. We should expect to see Esbjerg and FC Nordsjælland ascend in the table. Both teams are in the second half of the table despite having a TSR over 50%, in other words they dominate matches without getting properly rewarded for it.  SønderjyskE are not as bad as expected (as we pointed out in earlier stats reviews). Based on these numbers, they should be able to bounce back, but the point gap might already be too big (seven points). OB and Viborg are identified as the two worst teams in the league. There is a huge difference in the number of chances they create and give away. They need to reduce this difference otherwise the season could have an unhappy ending.

As we pointed out in the former reviews we are not enthusiasts of the total shots measure. We believe that the stat has some biased effects in the prediction of true chances, since it allows for a lot of hopeless long-range efforts. We believe that shots on target are a better, though not complete, measure of true chances. Therefore we place more weight on the next table, a ranking based on SoTR:

Look at the table. Does the ranking seem credible as a final standing? We think so!

FC Midtjylland should based on this ranking (and their current league position) be the favourite to win the league, although the race is tight for the top spots. Five teams have taken a clear lead when it comes to creating chances. Of them Esbjerg are the biggest underperformer and they should be able to jump some spots in the table.  FC Copenhagen and Brøndby should be able to pull away from the other teams in the middle of the current Superliga standing, while AaB are not to be underestimated. They are the real deal and could certainly clinch a medal. FC Copenhagen’s drop in ranking from TSR to SoTR is pretty significant and either are the FC Copenhagen players very wasteful or otherwise they simply have too many optimistic attempts that never hit the target. Back to the table, where a boring pack seems to emerge from Randers to FC Vestsjælland. For these teams a middle-of-the-road season is to be expected. Our analysis here predicts SønderjyskE and Viborg as the team to say adieu at the end of the season. SønderjyskE make a significant drop like FC Copenhagen. It seems plausible, SønderjyskE have not exactly been playing champagne football, and a lot of frustrated long-range efforts could have driven their TSR stat to an unordinary level. (If you are an unfortunate fan of SønderjyskE just forget you read this and go back to the TSR table). Viborg are our other relegation candidate despite of their current 6th position. They have the league’s largest difference in chance production and Mr. Dalgaard’s hot feet will not be able to save them forever.

To support our predictions we introduce the PDO statistic. The PDO statistic regresses to the mean and is therefore mostly driven by luck (see Grayson). Of course strong teams tend to do a bit better than weak teams over a season. This is natural since their strikers are typically better finishers and their goalkeeper has better reflexes. Therefore small differences from the average PDO of 1000 can occur even over time.

 

Viborg are based on this statistic a huge overachiever. They are scarily efficient both in scoring and saving. We cannot see this go on, even with Dalgaard in front. SønderjyskE are a huge underachiever, but you have to have in mind that their scoring difference is horrendous: -18. If SønderjyskE had had a normal PDO their scoring difference would have been -15. It is unlikely that the three goals could have made much difference in the table.

We give you an overview over the efficiency of the teams (baseline is league average). The teams in the lower left box have been unlucky, while the teams in the upper right corner have been fortunate. The teams should move towards the intersection.

 

If you would like to make some outright bets based on these statistics you can get the following odds:

The obvious choices:

FC Midtjylland to win – 2.70 at Betfair

Viborg to get relegated – 2.70 at Bet365

The “safe” one:

SønderjyskE to get relegated – 1.10 at Bet365

The long shot:

Esbjerg in top 3 – 8.00 at Unibet

It is important to have in mind that a lot can happen over the winter transfer window. The quality of a team can change significantly. FC Midtjylland have for instance already made an agreement to sell veteran Danny Olsen to AGF, while a team like SønderjyskE might make some purchases that can be either successful or failures. These statistics gives no sure conclusions, but they can help understanding the process. We intend to use the statistics for our future previews, but there should still be plenty of room for human assessment.