14/15 Quarter-season report, part 2

So, given that Dortmund isn’t doing very well so far, what are some of the causes of their troubles? In this post I’m going to dive a little more deeply into some of the underlying numbers to see if we can figure out areas of concern.

Factor 1: Bad luck

As badly as things have been going, the good news is that I’d attribute a lot of the side’s problems to bad luck. Let’s start with Total Shots Ratio. This Grantland link is a great explainer for the concept: http://grantland.com/the-triangle/what-is-total-shots-ratio-and-how-can-it-improve-your-understanding-of-soccer/. The short version: in football, teams that take a lot of shots (and prevent their opponents from taking a lot of shots) tend to have the most success. This can be summed up by a team’s Total Shots Ratio (TSR), which is calculated by taking the number a shots a team has taken and dividing it by the number of shots taken plus the number of shots the team concedes. The result is the percentage of the shots taken by the team in their matches. This value strongly correlates with match success; teams that take many more shots than their opponents naturally have more goal-scoring opportunities. Generally speaking, we would expect a team that underperforms their TSR to regress to the mean and improve over time, while a team that overperforms their TSR to regress to the mean and decline.

I've got a couple of tables here. The first is the actual Bundesliga tables through nine matches.

A few surprises here. Bayern at this point is by far the best side in the Bundesliga, and Wolfsburg and Leverkusen are perennial contenders for places in Europe. On the other hand, mid-table sides like Gladbach and Hannover are fighting for spots in the Champion’s League. Schalke and Dortmund are having disastrous seasons to this point.

Now, let’s have another look at the table, using each team’s TSR instead of points

Our understanding of the table is a lot different with this version. Only Bayern and Augsburg have the same rank in both tables. The biggest over-performer is Mainz, currently in 6^th while their TSR suggests that they should be in 16^th. As poorly as Schalke has performed this year, TSR suggests that they would be even worse, if not for good luck.

Most of the other sides are within five or so places of their TSR rank, and the difference is likely due to the relatively small nine game sample. The only club that has dramatically underperformed it’s TSR is Dortmund, currently in 15^th place, with a TSR that is tied for second. A TSR of .67 suggests that Dortmund is taking around two thirds of the total shots in their Bundesliga matches. In fact, they are tenth in the top five European leagues in shots allowed per game, and sixth in shots taken; they are one of only three clubs to place in the top ten in both metrics (the others being Bayern, and Juventus, currently in first place in Serie A).

Though the domestic season has gone very poorly to this point, the a big factor has to be a poor run of luck. Judging by TSR, Dortmund are dominating their matches; the shots just aren't quite hitting the back of the net so far. Simple regression to the mean would suggest that clubs like Mainz and Hannover are going to fall back to the pack, while Dortmund should expect to rebound.