Post Round 6 opponent-adjusted team ratings #AFL

Last week we introduced a fairly simple method of rating team strength based on statistics derived from inside 50s, which correlate strongly with winning teams (the premier usually sits near the top of the pile in these measures). The ratings are three simple statistical ratios:

  • Midfield Score (inside 50 ratio)
  • Offence score (efficiency of inside 50 conversions)
  • Defensive score (inverted efficiency of opponent inside 50 conversions)

These measures are then adjusted for opposition strength and converted to a percentage relative to the league average, which are presented in table format below.

r6 3.PNG

The above chart compares the opponent-adjusted Midfield and Offence scores. The further to the right a team is, the better their midfield (and other players) have been at generating inside 50s relative to stopping their opponents from having inside 50s. The Western Bulldogs, Geelong, Hawthorn, GWS, Sydney and West Coast shape as the strongest here.

The further up the team is, the stronger they have been at converting their own inside 50s into scoring shots and goals. Geelong, Hawthorn and GWS have been above average on this measure as well as being quite strong in their midfield. Adelaide, North Melbourne and Brisbane by contrast have been below league average in generating entries inside the arcs, but the most efficient (along with GWS) at scoring from them.

Now let’s look at defence:

r6 4.PNG

This chart instead compares inside 50 ratio with a team’s ability to stop scores. The midfield score is the same as the above chart. We can say, then, that the further to the right a team is, the less inside 50s they have conceded relative to the ones they’ve generated themselves. The higher a team is, the lower the conversion rate their opponents have had from their own inside 50s.

Comparing to the above chart we can see that of the six teams with the strongest midfield scores, only GWS and Geelong rate as above average on both their forward and defensive efficiency. Sydney appear as far stronger defensively and with a mediocre offence while Hawthorn’s decent forward efficiency is balanced by a much weaker defence.

Note also how much Brisbane – with a Forward score rivalling Adelaide and North Melbourne – suffer on the defensive side, relative to those clubs.

The full tables

Below are the full sets of figures and an overall ranking, where we can see the above information along with how opponent strength has impacted it:

r6 1.PNG

With their above average ratings in all three categories, GWS and Geelong currently look the strongest sides.

In terms of opposition, we can see that Hawthorn, Brisbane and Fremantle’s ratings all benefits from having faced strong sets of opponents. For example Brisbane’s 0.81 Midfield score is dragged up to 0.95 by the strength of their opponents in midfield, while their forward potency is increased substantially by the league-strongest defensive opponents they’ve faced. That is to say, Brisbane have been generating scoring opportunities at an above average rate, but the strength of the opponents defence improves that rating further still.

On the other side of the equation we can see that West Coast and Bulldogs’ relatively weak schedule hurts their ratings and that Geelong, North Melbourne, GWS and Sydney have faced a pretty average slate overall.

Lastly here’s the movements from last week. At this stage of the year the movements are fairly volatile, affected as they are not only by a team’s performance but that of their opponents:

r6 2.PNG

Melbourne, who we rated last week as fairly literally average, drop badly on a poor performance against St Kilda, falling a full 5 places after a 3% drop in overall rating. Their set of opponents have now had the weakest midfield scores in the league, devaluing their own Midfield rating.

Port Adelaide by contrast is a big riser – GWS and Geelong’s superb form has adjusted how we rate their past schedule, and they had a solid win as well.

Sydney’s rating falls the most of any side on the back of a close win against a Brisbane side which continues to be rated well below average in its midfield and defence. They do however remain as the third strongest side thanks to a league-best rating for defending inside 50s, and a strong midfield generating a good inside 50 ratio. So far at least, those two strengths have masked Sydney’s average inside 50 conversion efficiency – winning by sheer volume of opportunity .

GWS and Geelong jump the Swans with big movements of their own and sit virtually even at this stage at 115.5% of league average on these scores.



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