MLS Opta XI: The importance and limitation of stats

Opta released their MLS XI of the 2019 season. The team displays the importance of statistical analysis, but also the limitations of such processes.

How do you evaluate how good a football player is? It is not as easy it seems. Two different people, both of which understand the sport innately, can watch the same game and draw different conclusions regarding the individual performances they see. It is the nature of living in an opinionated, subjective world. Humans think different things.

This is where stats enter the equation. The number of goals a player scores is not dependent on your opinion. Similarly, the number of saves a goalkeeper makes does not change because of your perspective. This is the point of statistical analysis: to provide certainty to a subject area that is inherently uncertain.

Over the past decade, analytics has swept through the sporting world. And for good reason. It has helped teams win matches, provided greater analysis on players’ performance levels, and helped educate the watching fan base — sports fans are more intelligent than they have ever been.

This week, football analytics company Opta produced their Major League Soccer team of the season based on the stats that they have recorded through the 2019 campaign. There are some obvious names included. There are some less obvious ones. And there are some that are just downright false. You can see the full team here.

Without delving into the debate of who should be involved and who shouldn’t, because, let’s be honest, that is a rabbit hole that we might never get out of, I want to highlight the importance and the limitations of statistical analysis using the Opta MLS 2019 best XI.

Take their selection of Cristian Roldan. They included Roldan because he was one of only three midfielders in MLS to win possession over 200 times, to win possession in the final thrid more than 20 times, and to complete over 85% of his passes. They are interesting statistics, something that helps to provide a mathematical and comparable framework to an element of the game that is very difficult to analyse, general midfield play.

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But then take their selection of Minnesota United defender Michael Boxall. Their reasoning was that Boxall was the only player in MLS to win more than 65% of his tackles and duels with a minimum of 50 attempts in both. Sounds good, right?

Well, yes, but if you were to spend any time watching a Minnesota United game, you would very quickly recognise that Ike Opara is the superior defender. Winning a high proportion of tackles and duels is a good thing, of course, but you do not have to be highly capable in this area to be a capable defender overall.

Every good statistical analyst will tell you that any proper evaluation unequivocally requires an appropriate context. A number without context is meaningless. And this is where the limitation of stats in football comes. Using numbers is a good thing, but using them badly, without proper context and awareness, is not.

Whether you wholly agree with Opta’s analysis or not, I hope you can see that their statistical evaluations are helpful and insightful. They paint what is an uncertain picture using certain colours, and that is hugely advantageous. But there are limitations, and without acknowledgement of those limitations, such analysis is null and void.