I have spent the last few weeks chasing what I thought was a very elegant understanding between the number of possessions in a game and it’s result. I’m hesitant to call it a failure, but I have certainly left this exercise with many more questions than answers.
Essentially, my argument was that as the number of possessions in a game decreases, the liklihood of an upset increases. This is simply an extension of the fact that a weaker team is more likely to win against a stronger team in a single-game series than in a multiple-game series.
Despite finding that possessions per game seems to be normally distributed:
My first hint that I was wrong came in the fact that goals per game was actually negatively corrolated to possessions per game (albeit weakly). I expected at least a positive corrolation – perhaps even a strong one.
Then, I ranked each EPL team on the number of possessions per goal and also looked at the standard deviation of game-over-game possession efficiencies.
Poss. Per Goal
|West Bromwich Albion||134.6786||63.68292183|
|West Ham United||183.8837||61.57649119|
While possession efficiency expectantly corrolates strongly to league position, I was concerned with the large standard deviations. Increasing a seasonal scoring efficiency will obviously help a team in the long run, but seeing this play out on a game-by-game basis seems unlikely.
Here is a list of teams sorted by their average number of possessions per game and the associated z-score. The results here are interesting.
The league-wide average number of possessions per game was: 213.4105 and the standard deviation was 22.1311
Possessions Per Game
|West Ham United||208.0789||-0.24090771|
The outlier in Bolton Wanders with signifigantly the largest z-score is pretty interesting. If I saw a prototypical team such as Manchester United or Stoke in this situation, I wouldn’t be surprised. What’s up with Bolton?
Also, given the original premise that weaker teams want to decrease the rate of possessions (and conversely for strong teams), why do we see Manchester United, Manchester City and Chelsea occupying 3 of the lowest 4 positions in average possessions per game? Shouldn’t they be the teams that would benefit the most from increasing the rate of play?
The first thought that comes to mind is that stronger teams find themselves in winning situations more often, and therefore actually can benefit more from slowing the game down.
By looking at the total number of possessions that a team had in losing situations, divided by the number of goals scored from those losing situations, we can get a picture of scoring efficiency when we expect it is in the best interest of the team to push the rate of play. More importantly: how each team’s efficiency changes based on the game state.
|West Ham United||192.64||183.88||-8.76|
|West Bromwich Albion||146.00||134.67||-11.32|
While I was not surprised to see Manchester United’s efficiency improve from one goal every 98 possessions to a staggering one goal every 73 possessions when losing(a 34% change), I was incredibly surprised to find Chelsea and Liverpool bottom-dwelling. What would cause such an incredible disparity between top clubs?
This metric is a decent measurement of a team’s ability to chase a game. Apparently, this quality isn’t necesssarily required to finish in top league positions.
I wonder if I could find a corrolation between the number of fans leaving early and this derived metric!