David Wagner became the latest Premier League manager to get the sack (or leave my mutual consent) with his Huddersfield team at the bottom of the league. But will replacing him make any difference?
Arséne Wenger once famously said that the manager was perhaps worth a 10% performance gain and Chris Anderson & David Sally, in their excellent book ‘The numbers game’, showed that the best coaches are actually worth about a 15% gain.
So, when should changing the manager make a difference? Fortunately there is now quite a lot of data and some good analysis that can help clubs in making this decision.
A good starting point is to look at the relationship between playing staff wage bill and league finishing position (left. note this only until 2014).
The data shows a strong correlation between the two and in addition that it is very difficult to build a squad capable of winning more than 70 points in a season without having a top 5 wage bill. Indeed, in recent years the exceptions to the rule have been Liverpool and Tottenham (several times) and Leicester City in their title winning year. Other over achievers (in the sense of finishing higher than their wages would predict) have been Burnley and Bournemouth who have both finished mid table several times in recent years with basement wage bills.
With this understanding we can come back to David Wagner. Huddersfield Town had the smallest wage bill in the Premier League last season (left) so it is no surprise that they are bottom of the league this year. Indeed this would suggest that Wagner overperformed in avoiding relegation last season. Looking at the data you wonder what difference replacing the manager will have – certainly in the medium term once any short term ‘bounce’ effect has worn off.
So when do you replace the manager with a realistic expectation of improvement?
Manchester United this season were a great example. With one of the biggest wage bills in the league and languishing in 6th place a full 19 points behind the leaders it was clear that Jose Mourinho was underperforming for whatever reason and a change was justified.
Then lo and behold, with a new manager in place the team start to perform to the level they should be at based on the wage bill, winning 6 games in a row and climbing up the league table. There is a small caveat here in that 6 games are not as statistically reliable as a full season of results. With a win percentage, even over the last 5 seasons, of just over 50%, winning six in a row is like tossing a coin and getting heads 6 times in a row - not an everyday occurrence but not that improbable either.
In a future post I will take a look at what was happening at the underperforming and over-performing clubs that may explain the performance gap with some interesting implications for leaders of teams in business and other organisation settings.