How a Man’s Bad Math Helped Ruin Decades of English Soccer

Here at FiveThirtyEight, we tend to think statistics can add to our understanding of sports. (What a surprise!) From the more mature sabermetric movements of baseball and basketball to growing ones in soccer and hockey, evidence-based examination has led to new thoughts and ideas about the games we love.

But there can also be a dark side to analytics. Among other potential pitfalls, interpreting the numbers incorrectly can lead to terrible decisions or encourage habits that are hard to break, particularly given the added weight that conclusions carry if they appear to emerge from hard data. For an example, look no further than the state of English soccer after it began using what appeared to be a scientific strategy.

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This is part of our new podcast series “Ahead Of Their Time,” profiling players and managers in various sports who were underappreciated in their era.

In the latest installment in our documentary podcast series Ahead Of Their Time, we look at Charles Reep, the father of soccer analytics — and a guy who made one big, glaring mistake that changed the course of English soccer for the worse. But in order to arrive at his very wrong conclusion, he first had to radically transform the way people thought about consuming a soccer match.

There was no Opta back in 1950, no Total Shots Ratio, no Expected Goals. But there was Reep, who took it upon himself to attend every Swindon Town F.C. match that season — sometimes with a miner’s helmet on his head to better illuminate his notes — and meticulously scribble down play-by-play diagrams of how everything went down. More than 60 years before player-tracking cameras became all the rage in pro sports, Reep was mapping out primitive spatial data the old-fashioned way, by hand.

Poring over all the scraps of data he’d collected, Reep eventually came to a realization: Most goals in soccer come off of plays that were preceded by three passes or fewer. And in Reep’s mind, this basic truth of the game should dictate how teams play. The key to winning more matches seemed to be as simple as cutting down on your passing and possession time, and getting the ball downfield as quickly as possible instead. The long ball was Reep’s secret weapon.

“Not more than three passes,” Reep admonished during a 1993 interview with the BBC. “If a team tries to play football and keeps it down to not more than three passes, it will have a much higher chance of winning matches. Passing for the sake of passing can be disastrous.”

This was it: Maybe the first case in history of an actionable sports strategy derived from next-level data collection, such as it was. And Reep got more than a few important folks to listen to his ideas, too. It took him a few decades of preaching, but Reep’s recommended playing style was adopted to instant success by Wimbledon F.C. in the 1980s, and then reached the highest echelons of English soccer — channeled as it was through the combination of England manager Graham Taylor and Football Association coaching director Charles Hughes, each of whom believed in hoofing the ball up the pitch and chasing it down (and now seemed to have the data to back up their intuition). The long ball was suddenly England’s official footballing policy.

The trouble was, Reep’s theory was based on a fatally flawed premise. As I wrote two years ago, when discussing Reep’s influence on soccer analytics:

Reep’s mistake was to fixate on the percentage of goals generated by passing sequences of various lengths. Instead, he should have flipped things around, focusing on the probability that a given sequence would produce a goal. Yes, a large proportion of goals are generated on short possessions, but soccer is also fundamentally a game of short possessions and frequent turnovers. If you account for how often each sequence length occurs during the flow of play, of course more goals are going to come off of smaller sequences — after all, they’re easily the most common type of sequence. But that doesn’t mean a small sequence has a higher probability of leading to a goal.

To the contrary, a team’s probability of scoring goes up as it strings together more successful passes. The implication of this statistical about-face is that maintaining possession is important in soccer. There’s a good relationship between a team’s time spent in control of the ball and its ability to generate shots on target, which in turn is hugely predictive of a team’s scoring rate and, consequently, its placement in the league table. While there’s less rhyme or reason to the rate at which teams convert those scoring chances into goals, modern analysis has ascertained that possession plays a big role in creating offensive opportunities, and that effective short passing — fueled largely by having pass targets move to soft spots in the defense before ever receiving the ball — is strongly associated with building and maintaining possession.

 

It probably wasn’t entirely Reep’s fault when England flamed out at Euro 1992, or when they failed to qualify for the 1994 World Cup. But it couldn’t have helped that they were playing a misguided style, informed by well-meaning but faulty statistical principles.

Ultimately, Reep was a cautionary tale of the damage that can be done when stats go wrong. But he was also light-years ahead of his time for tracking stats in the first place. Even though his conclusions were wrong, his instincts were right. Now, national and club teams across the globe pay for massive amounts of data that, in one way or another, come out of the tradition of soccer analytics that Charles Reep helped start. As far as legacies in the game go, you could do worse.

via Hacker News http://ift.tt/2eJlX2Z

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