Tuesday, May 28, 2013

Goals scored and clean sheets: comparing historical averages to the season so far

The trend of scoring well below the historical average finally ended. Through the first 10 weeks of the season, defenders were king and forwards were more or less ignored. Many players opted to play 5-4-1 or 4-5-1 formations and lamented the fact that defenders were scoring far too many points relative to forwards. Three weeks ago, that all changed.

There were 2.86 goals scored per game over the last three weeks. (If we scored at that rate over all games this season, there would be 44 more goals scored this season than what have actually been scored). That brings the season average up to 2.48 GPG, still below the historical average. Over the last four years, we saw 2.57 GPG. If we simply apply the historical GPG to this season’s games played, we would have 303 goals - 10 more than we experienced. That isn’t too large to suggest any huge shift for our strategy. However, if we ignore the last three weeks and just look at how far behind we were during the first 10 weeks, we really see why I think it is time to divest from our defenders.

Over the first 10 weeks of the season, there were a measly 2.33 GPG (193 goals in 83 games). If we apply the historical rate of 2.57 GPG to those 83 games, we would have had 213 goals – 20 more than what we saw. That’s 100 points from goals alone and about 150 if you include assists at the historical rate. Most of those points would go to forwards. We’ll assume that about 60% (90 points) of them will go to forwards, 30% to midfielders, and 10% for defenders.

A mere 150 points doesn’t seem like it would make much a difference… and it really isn’t a colossal change. The big change comes when we look at the clean sheets. For this portion, I will assume teams use 4 defenders and a goalie, for 5 total “defenders”. 

So far this season, defenses have kept an astonishing 26.7% of possible clean sheets. Incredible. Through the first 10 weeks of the season, it was an even better 28.3% of possible clean sheets. Over the last four years, the rate of clean sheets is 13.7%. That means that teams so far this season are keeping clean sheets about twice as often as they have over the last four years. If we apply the historical rate of clean sheets to this season, there would be 32 fewer clean sheets this season than we’ve seen in reality (63). 32 clean sheets, times 4 points for a clean sheet, times 5 defenders = 640 more points earned by defenders this year from clean sheets than what would be expected based on historical averages. And just for fun we’ll add in the points lost (-1) for conceding two goals for each of the 20 more goals we would expect from historical rates and we get another 50 points that defenders have scored this year that they wouldn’t have. That is a total of 690 points defenders have earned this season above what is normal. That is HUGE and equates to 7.26 more points for each starting defender/keeper than what they were expected to earn.

Now I’ll apply these expected average adjustments from above (+2.37 for forwards and -7.06 for defenders) to the average score of the top 10 and top 25 for each position.

What to make from all of this? Defenders have been vastly outperforming historical averages; forwards have been slightly underperforming historical averages; and if we apply those averages to what has actually happened, top defenders should still be expected to outperform top forwards, but not by nearly as much as they have been this season. The assumption that those extra goals would be evenly distributed amongst all starting forwards is a bad assumption, because we would expect guys like Wondo, Henry, and Higuain to outscore guys like Tristen Bowen and Lionard Pajoy.

1 comment:

  1. Andrew, I love your work. I would like to bounce something off you that I am certain will be of interest to you. Please email me at phil@fiflasoccer.com so we can discuss. Thanks. --- Phil