AFL Rankings: Round 8 2020

St. Kilda’s improvement this season has been fuelled by its goal accuracy. Have the Saints been better or lucky?

The Saints come marching back

St. Kilda’s impressive win against Port Adelaide at Adelaide Oval in Round 8 moved it up to third on the AFL ladder. So far, this is looking like a significant improvement on last year’s fourteenth-placed finish, and the sixteenth-placed finish the year before that.

On the rankings, the Saints have gained more ranking points this year of any team except the Gold Coast Suns. The Saints have an average net margin this year adjusted for home ground advantage and opponent strength of +12 points (see chart below). This has been driven by impressive wins against Port, Richmond, and the Western Bulldogs. In their last 14 matches for 2019, their average adjusted net margin – also deflated to compare with this year’s shorter quarters – was -16 points.

St. Kilda has scored more points than any team so far this season besides Brisbane. However, in terms of scoring shots per game this year it only ranks tenth. Have the Saints actually improved by as much as the results suggest, or have they got a bit lucky? Or like Tim Membrey’s scissor-kick goal – is it perhaps a bit of both?

St. Kilda suddenly becomes deadly accurate

In recent years, the Saints have been somewhat let down by their inaccuracy when kicking for goal. So far this year, they have been amazingly accurate.

St. Kilda kicked 12 goals and one behind against Port Adelaide, making it the first team in the VFL or AFL in 120 years to win a match when scoring only one behind. Against Richmond in Round 4 the Saints kicked 15.3. Against the Bulldogs in Round 2 they kicked 14.4. That means in their three most impressive wins this season they scored 41.8, meaning they scored at an astonishing and seemingly unsustainable conversion rate of 83 per cent.

The Saints have generated good shots

Many AFL followers with at least a passing interest in more advanced AFL statistics would know of the concept of expected score, which is the score a team would be expected to kick given the location of their shots on goal. A really good resource for this is Stats Insider’s Shot Charting Explorer. This can help us work out if the Saints have been accurate in front of goal because they have been generating good shots, or because they have been converting those shots into goals at better rates than you would expect?

According to Stats Insider’s data, it is more the former. St. Kilda expected score this year given where they have taken their shots at goal from is higher than its actual score. The Saints’ actual scores were only slightly higher than their expected scores in their wins against the Tigers and the Bulldogs. They have still substantially improved their shot-taking from last year, but it is their shot-creating that has been really good.

Up to Round 7 the Saints had taken around 30 per cent of their shots at goal from zero to 24 metres out this year according to the Stats Inside figures, up from around 20 per cent last year (see table below). Less of their shots have come from the 25-49 metres range. Their accuracy is up by at least 10 percentage points from both the below 25 metres range, and the above 50 metres range.

Furthermore, the Stats Insider’s heat maps (see below) show that more of their shots have come from directly in front of goal rather than to the left or right, which is probably why their accuracy has improved. Last year’s heat map is fairly typical of most clubs in its spread around the 50 metre arc. This year’s heat map, once it gets near the goal mouth, is arrow-straight.

Straight shooting Jack

One player who is emblematic of the Saints’ improved goal accuracy is Jack Billings. In 2018, Billings kicked 14 goals and 19 behinds. In 2017 he kicked 23 goals and 36 behinds. West Coast’s Josh Kennedy kicked only three more behinds, and bagged 46 more goals. If Billings had been able to convert at the league average, then he would have added 1 or 2 more points per game to the Saints’ score – small in the context of the overall result, but a sizable proportion of the contribution of one player.

This year Billings has kicked seven goals and just one behind. His actual score of 43 has been 15 points higher than his expected score, according to Stats Insider. In contrast, he scored five goals less than his expected score in 2018, scoring a goal on about one-quarter of his shots from 25 metres or more.

A fair proportion of goal accuracy is random: one year’s straight shooter can be next year’s sprayer – even if you are Ben Brown. If the Saints can keep generating shots as good as they have though, they are on a fairly sustainable path.

AFL Rankings: Round 7 2020

This week: some teams seem to be separating themselves up the top from the pack.

Currently there is a (somewhat) clear top five

At the completion of Round 7, the top five teams are Port Adelaide, Brisbane, Collingwood, Richmond, and Geelong. Those are also the top five teams on the rankings (though not in the order). Isn’t that nice when that happens?

However, the form of those top five teams across the first seven rounds has been more varied than that neat dividing line suggests (see table above). Port Adelaide and Collingwood have been excellent this season, with Port having a percentage of 153.8, and Collingwood a percentage of 144.6. They are ranked #1 (Pies) and #2 (Power) in effective disposals and contested possessions. As noted here a couple of weeks back the Power went on a four-week tear to start the season. Meanwhile the Magpies had a good win against Geelong on the weekend, to go with their comfortable wins against Hawthorn, St. Kilda, and the Western Bulldogs.

The Brisbane Lions have been pretty good this year too, with their wins including a big one against Port Adelaide. However, their losses against Geelong and Hawthorn – with neither result being close (albeit way back in March for the Hawks match) – are a bit of a blemish on their otherwise strong form. The Lions rank second for inside 50s (behind Port), and first for intercept differential.

Richmond had been on negative ranking points for the year until its 54-point win against North Melbourne on the weekend. The Tigers are still ranked so high mainly on the strength of their premiership-winning form in the back half of last season. However, they did show some signs of being ‘the Tigers of old’ with their demolition of the Kangaroos, with a intercept differential of +12, an inside 50 differential of +23, and a tackle differential of +8.

Geelong sit just outside of the top four, and they have also been a bit patchy this season. The Cats’ wins against Brisbane and Hawthorn were pretty impressive, but they have also lost to GWS and Carlton, and snuck home against Melbourne. While they do not quite have the most effective disposals this season, they do have the highest effective disposal differential with their opponents. They are possibly ‘the fifth Beatle’ of this group, but given they were minor premiers last year and were 21 points up at half time in a preliminary final I’ve included them amongst this group of ‘contenders’ – for now.

What about the Eagles?

2018 premier and 2019 finalist the West Coast Eagles sit just behind these teams in eighth on the ladder, after their win against Fremantle in the Western Derby. The Eagles are seventh in the rankings, however they have accumulated no ranking points this year, and did not finish 2019 in the best of form either. They got fairly well beaten for three straight weeks while staying in Queensland, losing to Gold Coast, Brisbane, and Port Adelaide by a combined 122 points (see chart below). The Eagles are middle of the pack for effective disposals, contested possessions, inside 50s, and intercepts. They do however rank second in clearance differential.

West Coast has hit back a bit in the past three weeks with three easy wins, which has included 14 more goals and 57 more inside 50s than their opponents. Those wins have been good even if they have come against three of the bottom four ranked sides, with an average net margin adjusted for opponent strength of +25 points (see chart).

Maybe things will keep building for the Eagles now with an extended home run. Main players such as Josh Kennedy, Elliot Yeo, and Shannon Hurn who had not done too much so far this season have started to find some form, with Kennedy kicking four goals on the weekend. I think we would still want to see a good performance against recent (though famously vanquished) nemesis Collingwood next week however before we put the Eagles in that top group.

AFL Rankings: Round 6 2020

A significant proportion of home ground advantage in the AFL has probably been neutralised this season. For non-Victorian teams, this may the best year to be good, and the worst year to be ‘bad’.

In the most recent round of AFL matches, due to the restrictions resulting from the COVID-19 pandemic – particularly in relation to Victoria – no team played in its home state. This continues the pattern this year of more games taking place in ‘neutral’ territory, as teams have had to play for several weeks in ‘hubs’ due to border restrictions between Australian states. In the first six rounds of this season, I consider that 30 matches have taken place on ‘neutral’ ground, up from 19 in the first six rounds last season (I assign no home ground advantage for two Victorian teams playing at the MCG or Marvel Stadium).

With Victorian teams the most affected, non-Victorian teams could end up playing more games in their home state than away from it. Even if they do not though, having more games in neutral territory may be a bonus compared to previous years – that is, if you are a good team.

Good teams should want less home ground advantage

Home ground advantage brings volatility to results. If you are a good team, and the main outcome you care about is either win or lose, you want as little volatility in results as possible.

Let’s consider the example of two premiership contenders: the Yarras from Victoria and the Black Swans from Western Australia. Let’s assume they are both ten points better on average than everyone else, and that home ground advantage is two goals.

Now the Black Swans will play 11 matches at home with a two goal home ground advantage, and 11 matches away with a two goal home disadvantage. With plenty of Victorian teams in the competition though, the Yarras play ten games against other Victorian teams, six games in Victoria against non-Victorian teams, and six games outside of Victoria.

In this example, the Black Swans will start favourites only in their 11 home games. The Yarras will start favourites in 16 games. Basically the Black Swans’ home ground advantage strengthens them in games they are expected to win anyway, but they are at a disadvantage more often against poorer teams than the Yarras are. This is an extreme example, and the number of expected wins would be closer than this, but this gives the general idea.

On the other hand, if you are a ‘bad’ team you want this volatility. Home ground advantage may help you to get some wins against teams that are better.

The fixture is a fairly minor part in where your team finishes compared to ability. Since the AFL started there have been plenty of non-Victorian teams that have finished on top of the ladder, or on the bottom. Also, there is going to be so much uncertainty this season around where games and finals are played that this effect is going to be low down on any team’s concerns about fixturing. Still, every little bit helps if you are aiming for a flag.

AFL Rankings: Round 5 2020

AFL Rankings: Round 4 2020

Port Adelaide is now the #1 ranked team.

With four wins to start the 2020 season and a percentage of 236.3, Port Adelaide have moved to the top of the rankings this week, replacing Richmond.

Port’s four wins have been against Gold Coast, Adelaide, Fremantle, and West Coast. Those are currently the three bottom teams on the ladder, and 2019’s last-place side. Are Port’s good performances due largely to the quality of their opposition?

Port Adelaide’s four wins this season have come with a point differential of +199. After my adjustments for home ground advantage and opponent strength that is reduced to +170. That is still the best run of combined adjusted net margins in a stretch of four matches over the past year other than Richmond’s Round 23 and finals series. The rankings system arguably still overrates West Coast based on its form this season, but on that argument it would arguably still underrate Gold Coast.  

That places Port Adelaide as comfortably the best performed team so far this season, based on ranking points (see table above). They are also the best performed team over their past 11 matches, though most of that comes from their recent performances. In contrast, reigning premiers are high up in terms of ranking points over their past 11 matches, but have been below average so far this season.

Port’s biggest danger may be the bookmakers’ current premiership favourite Collingwood. Despite losing to GWS on the weekend, the Magpies are still rated highly from their big wins against the Bulldogs and St. Kilda, along with their performances last season. Port Adelaide and Collingwood lead the league this season in disposals, and are the two teams with a percentage of over 150. It has been a while since the former Magpies and the current Magpies played off in a major final, but perhaps this could be the year for it.

AFL Rankings: Round 3 2020

The GWS GIANTS may not be the attacking machine they are perceived to be.

In 2019, the Greater Western Sydney Giants famously made their first grand final, after three excellent wins in the finals series. While they ran out of petrol for the big one and were thrashed, they were still considered one of the leading premiership contenders ahead of this season. They had star players Stephen Coniglio and Callan Ward to return to a side that had just finished second.

On the rankings though they finished the season in ninth, rated about average. After consecutive losses to North Melbourne and the Western Bulldogs they are now ranked eleventh. Including last year’s Grand Final they have scored less than six goals in three out of their past ten matches.

Over the past 22 matches, GWS’ best stretch of form was those first few weeks of the finals, when they thrashed the Dogs, and beat Brisbane and Collingwood on the road (see chart below). Outside of that they’ve been average overall.

Despite player departures over the years, they still seem to have heaps of talent. But perhaps it is not quite as much as often thought.

The Giants get the ball a lot, but it is also about where and how you use it

When heading into the season Champion Data rated GWS’ midfield as only the twelfth-best in the AFL, the queue to ridicule Champion Data was almost as big as western Sydney itself. Ruckmen aside, on paper the Giants seemed to have the deepest collection of talent in the land rotating through the midfield: Coniglio and Ward, Josh Kelly, Lachie Whitfield, Tim Taranto, and Jacob Hopper, with Zac Williams and Toby Greene being able to push in and star as required.

Without going so far as to say Champion Data were ‘right’, there are a few things that place doubt on whether GWS’ engine room is as powerful as commonly thought. First, as Champion Data’s ratings capture, while Williams and Greene are excellent players and can play in the midfield usually they do not (Williams plays back, Greene forward). Whitfield also spends a lot of time starting centre bounces up forward and moving into defence.

Part of why GWS’ on-ballers are considered to be so strong is that they get a lot of possessions. GWS were second for disposal per game differential in 2019, close behind Collingwood (see table below). They were second in differential for contested possessions and clearances, and first for uncontested possessions. (They rank near the bottom in these categories so far this year.)

However, GWS ranked only sixth for scoring shot differential, and eleventh for inside 50 differential. The Giants may get a lot of the ball, but they don’t seem to get it down forward into dangerous attacking spots as often as a good team should.

Further, if we look at the Giants’ main ball-winners, a more significant amount of their work than other top teams is done in the defensive half of the ground. GWS’ top 10 disposal-getters averaged 3.14 inside 50s per game (per player) last year, but 2.91 rebound 50s (see table below). Other teams that Champion Data rated as having top midfields only averaged 2.36 rebound 50s among their top 10 disposal-getters. (North Melbourne’s midfield was also rated highly, but this was less of a ‘consensus’ pick among other experts, and is helped by having an elite ruck in Todd Goldstein.)

Included here would be defenders Heath Shaw and Nick Haynes, but again wingmen/half-backs Williams and Whitfield picked up a lot of their possessions away from their own goal. It does help them to defend very well, including in last year’s preliminary final, but it is a bit different to the attacking machine GWS may be perceived as.

Another reason why Champion Data rated their midfield so low is that some of their players were not exactly the best users of the ball last season. Tim Taranto (currently injured) led the league in clangers last year with almost five per game, and Hopper, Shaw, and Greene averaged about three to four per game each. Given that Taranto and Hopper are two players that spent most of their time in the ‘guts’, the perception of GWS’ midfield strength may still be somewhat ahead of their young players’ development.

As last year’s finals series showed the Giants can still be very good. But we should perhaps not be that surprised if they cannot make it back to the Grand Final this season.

P.S. Essendon and Melbourne, who had their match postponed this week after the Bombers’ Conor McKenna tested positive for COVID-19, are treated as having a bye for the purpose of the rankings. Their ranking points can still change slightly as their past results are re-assessed based on how other teams have performed this week – e.g. Melbourne’s win against Carlton is rated as slightly better given the Blues’ win this week against Geelong.

AFL Rankings: Round 2 2020

This week: Collingwood and Richmond again ensure that neither team wins, and how ‘bad’ are the Crows?

Collingwood and Richmond fight each other to a stalemate

After a three-month hiatus due to the COVID-19 pandemic, the AFL 2020 season resumed last Thursday night with a ‘blockbuster clash’ between Melbourne’s two current heavyweight clubs, Collingwood and Richmond.

The match was as close as many were hoping for, with the teams playing in their first draw since 1917. The scoring on the other hand was probably not what many were hoping for, with the two teams combining for just 72 points – the lowest combined game score since 1999.

Quarter lengths have been reduced this year from 20 minutes to 16 minutes each (plus time-on), and therefore scores are expected to be lower. And each team did have about 80 per cent of the disposals that they had on average last year (see table below). Yet they only had about 50 per cent of the scoring shots. What happened?

For many viewers, the enduring memory of the game’s second half is probably of Richmond booting the ball into their forward line, being spoiled by the Collingwood defenders, and then the Magpies chipping the ball back only to be repelled by a wall of Tiger tacklers, who then pick up the ball and boot it forward … with the the whole cycle repeating again.

Each team had about as many turnovers as they had on average last season in longer game time (see table above). After accounting for game time Richmond had a lower ratio compared with last season of effective disposals, handballing less and kicking more. Collingwood had a higher ratio of one percenters (spoils, smothers, etc.), led by backmen Darcy Moore and Jeremy Howe with nine and eight respectively. Richmond had a much higher ratio of tackles, with ruckman Ivan Soldo recording nine(!), and midfielder/mid-forwards Trent Cotchin, Dion Prestia, Shane Edwards, and Shai Bolton recording five or more each.

It was the football equivalent of putting a pox on each other’s house. Which, given Collingwood and Richmond’s history with each other, and the horrible standstill the world has been brought to this year, was perhaps a weirdly appropriate result.

Are Port Adelaide that good? Are Adelaide that ‘bad’?

For the first time, some fans were allowed to attend an AFL (men’s) match this season, as about 2,000 people watched Port Adelaide take on Adelaide before both teams head off to the Queensland ‘hub’ for a few weeks. Fortunately most of those were Port Adelaide fans, as the Power smashed the Crows by 75 points, giving them two wins so far by a combined total of 122 points.

Is Port Adelaide a ‘top four side’? Or is it just that Adelaide is a ‘bottom four side’? Perhaps both. When this blog checked in on both teams before last season’s first Showdown the two sides were fairly even, and about average. By the end of the season, Port Adelaide was still rated about average, but Adelaide had fallen away somewhat. This season, that disparity has become even bigger.

Port Adelaide’s past six matches have been overall fairly impressive, with an average net margin adjusted for opponent strength and home ground advantage, and adjusted to 16 minute quarters, of 24 points (see chart below). Apart from their two big wins this season the Power finished last season with comfortable wins against Essendon, Sydney, and Fremantle, with a big loss against North Melbourne their only blemish. None of those teams they beat are probably among the top sides, but Port is getting the job done well.

In contrast, Adelaide’s average adjusted net margin over their past eight matches is -24 points (see chart below). After their massive win against Gold Coast last season, the Crows lost to Essendon and Carlton, and got well beaten by Collingwood at home. Their best performance over that period was a close loss to West Coast in Perth. Only the Gold Coast Suns – who actually had quite a good win on the weekend – have fared worse in that time.

As it was last season, Port Adelaide’s performance is still being powered by their work in the midfield, as they rank first in disposals and inside 50s and second in clearances. The Crows meanwhile rank at or near the bottom in those categories, despite having Rory Sloane and the Crouch brothers. The problem for the Crows is that after their three primary midfielders the cupboard is fairly bare. Meanwhile Port’s Travis Boak had plenty of support from his midfielder-forwards, most notably second-year player Connor Rozee who had eight clearances, five inside 50s, and six tackles. Other young players like Xavier Duursma and Zak Butters were not half-bad either, and veteran Steven Motlop had one of his finest games since moving to the club.

Port Adelaide now sits fifth on the rankings. Adelaide sits fourth-last. On the evidence of the weekend and other recent matches, that seems a fair reflection of where both teams are currently at.

AFL Rankings: Round 1 2020

My AFL Rankings are back for their tenth season.

Anything major happen while they were gone?

...

OK – so with the COVID-19 pandemic, there have been some changes to the 2020 AFL season. The home and away season has been reduced from 22 matches per team to 17 matches, and the length of quarters has been reduced from 20 to 16 minutes.

I spent some time between seasons making significant changes to my rankings Excel file. Preparing all 23 rounds now seems a bit like a waste of time, at least for this season. On the other hand, my changes to the file made it much easier to adjust my rankings for the shorter quarters.

I’ve adjusted down all 2019 margins and home ground advantages to 80 per cent of their previous values, to reflect the shorter quarters this year (though there are arguments to adjust the home ground advantage down further). This did not affect the order of teams, before Round 1.

Anything interesting happen in the actual matches?

Collingwood had a good win over the Western Bulldogs in Round 1, by 52 points. That moves the Magpies up from seventh to second in the rankings, and the Bulldogs down from fifth to eighth. After Richmond at the top it’s all pretty close, so teams may move up or down several spots each week over the first few rounds.

The tips

Here are my predictions for the next round of AFL matches. I have adjusted my probability distribution for the shorter quarters as well.