AFL Stats That Matter: what are the real performance indicators?

Fourteen rounds down. Nine to go.

At this point we’ve got enough data to tell us which clubs are bad, good and indifferent.

117 matches of football - or 468 quarters of football if you really want to rummage through the weeds - is certainly enough of a sample size insofar as which stats are signals, and which are merely noise.

And so, without further ado, let's take a ride across the statistical landscape.

CLEARANCES AREN’T EVERYTHING WE THINK THEY ARE

Football fans love the notion of winning in the trenches.

There’s something romantic about muddied footballers putting their head over the ball, bravely extracting the footy and advancing their team’s position.

The only problem is, the idea of winning at the stoppages is quickly losing its lustre.

Port Adelaide sits on the top of the clearance differential ladder (+6.4), and certainly used it's +16 advantage to the fullest during their Round 14 upset of Geelong.

Yet, outside of Port, clearance differential isn’t providing us with a substantially clear picture of who’s good and who’s not. 

Melbourne (+4.2), Essendon (+3.6) and the Bulldogs (+3.6) presently occupy positions two through four on the clearance differential ladder, yet have a combined 15-24 record on the season, with all three extremely unlikely to play AFL Finals this season.

Conversely, Geelong (-2.5) and Collingwood (-0.2), who have been the league’s two best teams all season both possess negative clearance differentials in 2019, and are in the bottom half of the competition for the metric.  

And so the question is, why is clearance differential not holding up?

One theory is that the competition’s better teams simply aren’t devoting many resources to an area of the game they believe isn’t an imperative.

When Richmond won the AFL Premiership in 2017 the Tigers were a team who continually lost the clearance battle (-1: 11th in the league), but who were quite comfortable with their air-tight structures, their ability to intercept possession, and use their damaging foot skills around the park to hurt the opposition.

Dominating at the stoppages simply wasn’t a priority with their playing list, and neither is it this season for the league’s very best.

While the likes of Melbourne, Essendon and the Bulldogs take comfort in their collective hard-ball winning efforts, it’s labour which, for the most part, has been very much in vain.

DISPOSAL EFFICIENCY IS PROBLEMATIC AT BEST

The following is a team who wins the ball at the coalface with an amazing clearance differential of +3.6, and an inside 50 differential of +5.8 - placing them third in the league for I50 differential.

It’s a club whose awful goal-kicking, and general wasted opportunities is a source of great frustration for its fan base, with the general perception being that sloppy skills are routinely letting them down.

That team is the Western Bulldogs. 

Their disposal efficiency is 75.1%, which is the AFL's very best mark.

Confusing, right?

Who’s second in this key performance indicator? North Melbourne. 

They removed their coach a few weeks ago, have a 5-8 record, and - like the Bulldogs - have spent the bulk of the season closer to the foot of the ladder.

So is disposal efficiency simply a useless stat? Not entirely, though it is a highly problematic one.

Disposal efficiency - at least in terms of the way it is collated by the AFL - is troublesome as it doesn’t take into account how a team structurally prepares, while it provides no indication whatsoever on where (ie; what part of the ground) this apparent efficiency is taking place.

Take Hawthorn as an example. 

During their Premiership era, the Hawks were the league’s undisputed champion where disposal efficiency was concerned.

Their game plan was built around Clarkson’s ‘death by a thousand cuts’ mantra, which made maximum use of the team’s excellent skills by both hand and foot. They even inspired a comparison to FC Barcelona.

Even now, disposal efficiency remains a hallmark of Clarkson’s football philosophy, and in a season where the Hawks are decidedly ordinary and unlikely to play in September, they still boast a 73.6% disposal efficiency rate, good for fourth in the league.

Yet, here’s the thing. 

Geelong, who are the league’s best team as it stands - a game and percentage clear at the top of the AFL Ladder after Round 14 - losers of just two games this season, have a 72.1% disposal efficiency which is just middle of the road and enough for 10^th in the AFL.

Does this indicate the Cats have poor foot skills?

Not at all, though it would have plenty to do with the gameplan the Cats employ, which is not nearly as motivated by chipping away patiently around the defensive arc, with a much more long-ball orientated attack seeking to maximise Tom Hawkins’ beastly one-on-one ability.

Geelong also know that should the ball hit the ground, the likes of Luke Dalhaus, Brandon Parfitt and Gary Rohan are such excellent pressure-forwards that they’re very likely to keep the ball inside their attacking zone once they get it there.

Geelong laughs in the face of tiki-taka AFL. 

It might earn them their fourth premiership in 13 seasons.

METERS GAINED DIFFERENTIAL

Now, this is a stat you can hang your hat on.

Since meters gained began being charted, it’s continually had the strongest correlation with success.

And with a sport played on such vast expanses as AFL stadiums, it really shouldn’t come as a surprise that possession and territory is proving to be a massive component of your team’s chances of winning.

Where are the Cats ranked in terms of meters gained differential? 

You guessed right, numero uno, at +407m.

In fact, the top five ladder positions this season all correspond with the competition leaders in meters gained differential.  

Meters gained differential speaks directly to all facets of your team and it's style of play, and provides a picture of who is monopolising the field position game.

The two worst teams, and by some margin for metres gained differential are Carlton (-434m) and Gold Coast (-457m) and there’s not a soul who’ll argue that those two are anything but the league’s two worst.

From 2015-2018 there were 21 cases of a team achieving a +200 meters gained differential over the course of the season. 20 of those 21 teams made the AFL Finals. 

Only Melbourne in 2017 missed September action, and that was by percentage only.

In 2019, there are presently three teams with a better than +200 meters gained difference on the season. Geelong (+407m), GWS (+361m) and Collingwood (+251m). 

These just happen to be the competition’s three best teams.

Long live meters gained differential. 

Long may you continue to correlate so strongly with success.

MARKS INSIDE 50 DIFFERENTIAL

Almost as reliable as metres gained differential in terms of shining a light on the league’s best teams, the marks inside 50 metric is all about optimal shot creation, and shot suppression.

'Marks inside 50 differential' speaks directly to a team’s ability to set up an unmolested shot on goal attempt, as well as keeping the opposition from doing similar on the defensive side of the ball.

The leader of the pack in this realm is Collingwood, who also put pay to the notion that marks inside 50 are all about having a traditional key forward target.

In fact, the list of names who lead the way for Collingwood’s marks inside 50 are all non-traditional key forwards, such as Jordan De Goey, Jaidyn Stephenson, Jamie Elliot and Will Hoskin-Elliot.

Marks inside 50 differential also speaks strongly to a team’s midfield, and its ability to both provide optimal delivery to set up forward opportunities, as well as its ability to pressure and shut off clean flow going the other way.

Six of the eight teams who are presently in the top eight are all doing extremely well in this key indicator.

Just three of the last 18 AFL Grand Final teams have been ranked outside of the league’s top six for marks inside 50 differential.

CONTESTED POSSESSION STILL MATTERS

We mentioned earlier the problems associated with the 'hard footy' narrative that surrounds clearances, but winning the contested football doesn't speak to a part of the game that’s confined to a place and time.

Unlike clearances, contested possessions can be won and lost on any part of the field and at any period of a game, which makes for significantly more data points for analysis. And, we continually see a strong correlation with success in terms of contested possession differential. 

The best teams in the league in this statistic, Geelong (+11.8), GWS (+12.1) and Collingwood (+6.1) are all extremely strong at winning the contested ball.

Since 2010, we have 11 examples of teams who achieved a +10 contested disposal differential average over the course of a season. Nine of those teams found themselves playing on Preliminary Final weekend.

The AFL's increased statistical output is proving both a blessing and a curse for the broader AFL community. While it's wonderful having access to a colourful and diverse range of metrics it's also increasingly important to assess which statistics correlate with winning, and which numbers are merely providing convenient background noise. 

As it stands, meters gained and marks inside 50 differential are providing the strongest link to success - with a decade of data painting a rather clear correlation to winning both games of football, and, ultimately, AFL Premierships.

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