Don't be so quick to blame the coach for your team's poor play

At times, it seems that coaches in professional sports are shuffled more often than the decks at Vegas blackjack tables. And when the cards finally land, the hand can be a raw deal: with even a hint of distress, managers take heavy fire from team brass, sponsors and fans, all of whom have different stakes at risk and their own set of expectations for success.

If things go badly enough, teams may even dismiss a coach midseason, in a desperate attempt to bring the squad back from a season in freefall.

But a group of German football fans, who just happen to be statistics and sports science experts, suggests that it's time to rethink the all-too-familiar blame game.

Pouring over 46 seasons of German football league data, Andreas Heuer and colleagues from the University of Muenster and the University of Kassel have published results in the journal PLoS ONEshowing that a coach only contributes a small fraction to a team's overall success, and such midseason coaching changes have absolutely no effect on the team's future performance.

Instead of using the team-ranking system established by FIFA, where victories earn three points in the standings and ties get one, Heuer and his team followed guidelines he defined with co-author Oliver Rubner in 2009, when they argued that a better measure of a team's impact, or fitness, was the difference in the number of goals the two teams scored in a particular match.

Analysed this way, a team's fitness remains relatively constant throughout the season. After all, players aren't going to make Herculean gains in ability in just a few weeks' time. Rather, midseason soccer team fitness is more likely affected by variables such as weather conditions, injuries and even the number of red cards accrued.

The researchers found that when you plot the goal differential of teams who fired their coach midseason, it appears (at least at first glance) that these teams do get better.

But Heuer argued that this is simply an artefact of team that has fallen on hard luck. As any fantasy sports obsessive can attest, the chance that these down-and-out teams will eventually do better is high, regardless if they get a new coach or not.

So, to really compare apples to apples and provide a clearer picture of what effect a new coach has on a losing team, Heuer thought it better to identify suitable control groups -- teams that had bad luck, but stuck it out with their current coach for the rest of the season -- and compare them to teams that handed their coach a pink slip when times got tough.