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