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.

Wednesday, April 25, 2018

AFL Power Rankings: Round 5 2018

Five rounds into the 2018 season the majority of teams have three or more wins. But which of them are really above average?
If you were just looking at the AFL ladder at the moment it might be a little hard to tell which teams are actually the strongest finals contenders in 2018. Twelve teams – two-thirds of the league – have won three or more of their five matches so far. But which teams, once you take into account their fixtures so far, have actually been the most impressive? And which of them look the most likely to sustain their good performances?
The Power Rankings were designed to answer exactly these types of questions. It differentiates strong wins from narrow ones, and strong opponents from weaker ones. Clearly, as you can see from the table above, it still rates Richmond and Adelaide highly, and doesn’t think much about Gold Coast’s credentials. Also it’s not yet convinced about teams like North Melbourne or Fremantle, despite some impressive wins from both teams this year.
For teams like North Melbourne and Fremantle, some of this scepticism comes from their relatively poor performances in 2017. Based on their 2018 performances alone most of the teams that have won three or more matches in 2018 have been at least decent. With the exception of Gold Coast the average net margins in 2018 of all these teams, adjusted for home ground advantage and opponent strength, have been at least near zero (see table below). Further, of the rest, Fremantle is the only team I’d say hasn’t yet shown the potential to stick with the others.
We can divide these sides into four groups: “proven to be good”, “could be good”, “probably not above average”, and “well below average”.
“Proven to be good”
The first group of sides should be fairly uncontroversial – some ups and downs aside they have been the consistently best-performed teams over the past year or so: Richmond, Adelaide, Sydney, Geelong, and GWS. They were the top five sides last year, and have all put in at least a couple of good performances so far in 2018.
“Could be good”
On 2018 form alone Hawthorn, Collingwood and West Coast have been about as good as the above sides, with a couple of impressive wins each and generally decent performances. What keeps the Power Rankings from rating them as highly for now is that they were only around average last season. (West Coast finished sixth after the finals, but just barely made it into the finals series.)
Port Adelaide was a good side last year, their struggles against top sides notwithstanding. However since their great win in Sydney in Round 2 their performances over the past few weeks have been below average, and it’s not clear that they are one of the better sides anymore.
North Melbourne is a more complicated case. They were clearly a below average side last year, and have lost to Gold Coast and Melbourne this year. And two of their three wins have been against ‘bad’ sides in St. Kilda and Carlton. However those wins were thrashings and being able to beat up on ‘bad’ sides – despite the ‘flat-track bully’ stigma – is generally a good sign that you are no longer a bad side yourself.
“Probably not above average”
Fremantle was well below average last year, and have not beaten an above average side so far in 2018. But they do at least appear to be much improved, particularly with their big win against the Bulldogs on the weekend. They are around average on 2018 form alone.
“Well below average”
Gold Coast did start the season well, with wins against North and Carlton that were good enough to offset them being against below average sides. But their trips to Perth did not go well, and their latest win was a narrow one against lowly-ranked Brisbane. They may already have enough wins now to not finish last, but I don't expect the Suns to trouble the other finals contenders this year.

Sunday, April 15, 2018

AFL Power Rankings: Round 4 2018

After four rounds of the 2018 season there is no undefeated side in the AFL, and so far no dominant one.
For the first time since 1997 no AFL team is undefeated after four rounds, which suggests that no side is ‘running away’ with the competition. The rankings suggest this too, with the highest-ranked sides Richmond and Sydney having about four goals worth of ranking points, generally the mark of a really good but not great side. (A big yeah! though from this Tiger supporter for Richmond reaching the top of the rankings – the first time they have done so since I started them in 2010, and a long way from where they were when they started.)
Looking back over the rankings since 2010 the ‘great’ sides have tended to get 33 or more ranking points by the season’s end. (See table below – I’ve adjusted the historical ranking points so the sum across teams for each season adds to zero, consistent with my current method.)
That cut-off is a little arbitrary, but it includes the teams that many AFL followers would consider as the truly ‘great’ sides over that period: the big Collingwood-Geelong rivalry of 2010 and 2011, the Hawthorn dynasty of 2012 to 2015, and the Sydney Swans Grand Final sides of 2012, 2014, and 2016 (even though the 2010 Geelong and 2016 Sydney sides were ‘upset’ along the way).
The next tier of sides, with 25 ranking points of more, includes some Grand Finalists and even a premier. But it also includes some pretty good seasons that didn’t get close to a flag, such as Carlton in 2011, West Coast in 2012, and Adelaide in 2016. This is about the level that the top sides sit today (and last year too), making the premiership race more open than usual.

Even if we just look at 2018 form adjusted to a full season’s worth of ranking points no side emerges as dominant, which is reflected in the evenness of the ladder. Hawthorn is the closest with about 32 ranking points, but 60 per cent of their 2018 ranking points come from their win over Melbourne this weekend, and the Hawks were hardly dominant against Geelong and Richmond (indeed, the Tigers beat the Hawks reasonably comfortably).

A dominant team could always emerge, and just hasn’t got going yet – remember that the 2014 Swans, minor premiers for that season, lost to bottom-ranked GWS in its first match. But if they don’t then we could be in for a season of ever-changing flag favourites.

Sunday, April 8, 2018

AFL Power Rankings: Round 3 2018

Though they have taken things down a notch so far in 2018 St. Kilda’s performances have been heading in the wrong direction for some time now.

AFL results in 2018 have so far probably been in line with many people’s expectations. This seems relatively unusual for this early in the season, when there usually seems to be at least one team rising upwards or falling apart.
One possible exception though is the performance of St. Kilda. The Saints started the season with a relatively unconvincing win against the Brisbane Lions, and have followed that up with big losses against North Melbourne, and Adelaide at home. Over the first three rounds of 2018 no team has had a bigger downgrade in its ranking points as the Saints have.
Before the season started I would have rated the Saints as ‘about average’. But perhaps their overall ranking at the end of 2017 was a bit misleading. When you look more closely at their performances over the latter half of 2017 it emerges that they generally had more ‘below average’ performances than ‘above average’ ones. (See the chart below, which shows St.Kilda’s net margins over its past 22 matches adjusted for estimated home ground advantage and opponent strength.)

St. Kilda started 2017 off well, and a passing of the baton looked to have occurred when they demolished Hawthorn by 75 points in Round 6. But after that the good performances have actually been few and far between. What may have partly hidden this trend was the Saints’ impressive 65 point win against eventual premiers Richmond in Round 16 – a result that led to them being well-rated at the time but is harder to believe in retrospect. Without that win the Saints’ average adjusted margin would have been that of a ‘below average’ side in the back half of 2017, and might now be considered a truer reflection of where they were at.

Of course, as Hawthorn itself proved after their own downward slide in late 2016 and early 2017, clubs can pretty quickly turn things around. Consider that, when I was originally planning this week’s post, I was going to throw in the Western Bulldogs as another example of a team that had carried on its ‘below average’ performances from late-2017 … and then the Dogs went out and had a good win on the weekend. (Not that this completely invalidates the longer-term trend, but it didn’t make the narrative as neat anymore.) So Saints’ sceptics shouldn’t be overly smug yet – and St. Kilda has shown patches of good performance over the past year … just not for a while now.

Monday, April 2, 2018

AFL Power Rankings: Round 2 2018

GWS and Port Adelaide have had good starts to the 2018 AFL season. But should we rate them yet as highly as 2017’s late-season powerhouses?

After two rounds of the 2018 AFL season the four undefeated sides are Greater Western Sydney, Port Adelaide, Hawthorn, and Gold Coast. GWS and Port in particular are getting some consideration as premiership contenders on the back of their early season form.

The Power Rankings though still rate the Giants and Power slightly behind last season’s top triumvirate of Sydney, Adelaide, and Richmond. Why are they not rated as highly? Should they be?

GWS and Port have earned by far the most ranking points so far in 2018. Although note that most of those points really just come from one of their two matches – for GWS it is from last week’s thrashing of the Bulldogs, and for Port it is from this week’s impressive win in Sydney.

The Power Rankings do place their highest weights on those past two matches, but they also still place a fair amount of weight on results from late-2017, including last year’s finals series. To many (including myself) the details may have become a bit hazy in the break between seasons, but each of the Swans, Crows, and Tigers finished off last season much more impressively than the Giants or Power.

In their past nine matches, based on their net margins adjusted for estimated home ground advantage and opponent strength, the Swans have had six performances that I would categorise as ‘good’ (see table above). These are: their win last week against West Coast in Perth, their finals win last season against Essendon, their thrashings of Carlton and Fremantle in the late rounds of 2017, and their wins last year in Adelaide and Geelong. (Conversely the Swans also had one ‘poor’ performance in that period, which was their big finals loss to Geelong.)
The Crows have had five performances I would consider as ‘good’ in that time – their win against Richmond this week, their finals wins against Geelong and GWS, their thrashing of Port in last year’s Showdown, and a comfortable win against Essendon in Melbourne. Fewer AFL followers need reminding of how the Tigers finished off 2017 – they easily beat Fremantle and St. Kilda in the final two rounds before mowing through Geelong, GWS, and Adelaide on their way to the premiership.      
The Giants and the Power just don’t have that lengthy a record of strong performances recently. Apart from thrashing the Bulldogs last week the Giants’ only really impressive performances in their past nine matches were their thrashing of West Coast in last year’s finals and, also from 2017, another handy defeat of the Bulldogs. For the Power it was the win against Sydney this week, and last year’s 115-point final round demolition of Gold Coast.
Now if I weighted the rankings differently to place much more weight on the past two rounds then GWS and Port would come out on top. So arguing or thinking that GWS and Port are the two best sides at the moment is really just placing a relatively high weight on the two rounds that have happened so far in 2018. Or put another way, it is valuing form in the new season more highly relative to what happened during the finals of the old season.     
In any case though the Giants and Power are good sides. And when one is listing the premiership contenders in 2018, both should be considered amongst the sides with the strongest chances.    
The Gold Coast Suns, despite winning their first two matches, should not be considered amongst the top teams. The Suns beat North Melbourne and Carlton, who are both lower-ranked sides, although their margin of victory against Carlton when playing away was somewhat impressive. Because of the Suns’ dreadful end to 2017, it will be a while before the rankings even consider them as just mildly below average. Again if one placed a high weight on new season form they would be rated more highly. At the least though, on the evidence so far, the Suns look to have improved a fair bit in 2018.