Monday, April 30, 2018

AFL Power Rankings: Round 6 2018

Fremantle, Hawthorn, and North Melbourne are rated as the biggest improvers so far in 2018. What are they doing better?
This week I had added back into the Power Rankings table each team’s change in Ranking Points over the 2018 season to date, as we are now enough weeks into the season for it to be somewhat meaningful.

So far in 2018 the Power Rankings rate the biggest improvers as Fremantle (+11.2 ranking points – see chart below), Hawthorn (+10.1), and North Melbourne (+9.3). Freo and North are still rated as ‘below average’ mainly due to their performances in 2017, while Hawthorn has gone from ‘average’ to ‘good’.

The biggest declines in performance, according to the Rankings, are from St. Kilda (-11.9), Carlton (-10.0), Essendon (-9.4), and the Western Bulldogs (-9.1). St. Kilda, Essendon and the Bulldogs have gone from being rated ‘average’ to ‘below average’, while Carlton is now ‘well below average’.

I could end it there for this week, but I thought it would also be informative to borrow (or filch) a concept from the excellent HPN Footy website to see in which parts of the field these teams have improved. Basically HPN rate each team’s midfields, offence, and defence as follows:
·       Midfield – how often a team gets the ball into attack compared with how often their opposition gets it into attack;
·       Offence – how often a team scores when it gets the ball into attack;
·       Defence – how often a team stops the other team from scoring when the other team goes into attack.
‘Attack’ here is defined as getting the ball into your 50 metre zone, which is a statistic that is commonly available. These ratings are obviously not meant to explain everything that goes on in a football match, but they do give a good, quick overview of where each side is generally ‘winning the battle’. Note that I’m going to vary slightly from the HPN method here, in that I’m going to use points per inside 50 to measure offence and defence and not adjust for opposition strength, but I don’t think it will matter too much for showing where each team has improved or declined.

Based on these ratings, the biggest improvements from Fremantle and Hawthorn have been their ability to get the ball into attack (their ‘midfield rating’). For North Melbourne it’s been their ability to stop the other team scoring once it gets into attack – a topic which was covered in much more detail by HPN itself last week.

For the big decliners, St. Kilda has been relatively awful in scoring once it gets the ball inside its own 50 metre zone. Essendon has been mainly worse at defending, the Bulldogs at winning the midfield contest and defending, and Carlton at both kicking goals and stopping them.

Of course teams don’t just go through changes in performances between seasons, but also changes within them. We’ll see the Rankings’ cross-season comparisons swing about many times throughout the year, but this shows which teams appear to be headed in the right direction.

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