What does the AFL ladder mean not even one-third of the way through a season? Well, quite a bit, actually, if you subscribe to what has proved a handy tool over the years for those of us in the business of football prognostication.

It’s the “Round 7 Rule”, and while many in football prefer to sneer in the face of history whilst mouthing platitudes about creating their own, it’s a measurement which has been on the mark far more often than not.

In a nutshell, it says that if you’re not in the top eight at this stage of the season, your chances of being there at the end are limited.

In 17 completed AFL seasons since 2001, there’s been a total of just 21 changes to the top eight as it stood at this point and the start of the finals, an average of little more than one team per season.

Only six times in those 17 years has there been more than one change, only once have three teams changed, and in that season of 2012, those teams which came into the eight were at least by now sitting in ninth, 10^th and 11^th positions on the ladder. And of the 21 teams in total to force their way in, 16 were no worse than one game off the pace by now.

Of course, there’s exceptions to the rule, none more obvious than Sydney last year, which at this same stage had just won its first game, already three wins off the pace, but which would go on to win 14 of its last 16, finishing sixth on the ladder.

The Sydney Swans was the greatest exception to the ‘Rule’ – making the finals after losing its first six games in 2016. Photo: Getty

Richmond in 2014 was two games outside the eight by now but would get there by winning its last nine in a row. And St Kilda in 2011 was by this point two-and-a-half wins outside, but would end up reaching September for a fourth season on end.

Even in those Lazarus-like efforts there’s been a considerable caveat, though, namely in the effort expended just making it. The Tigers and Saints would exit their finals campaigns immediately, and Sydney last year, for all the momentum the Swans had built, ended up drummed out of September by 10 goals in week two against Geelong.

So what does it all mean in the context of the 2018 season? Well, perhaps a few pointers at least. Like that however unlikely seemed West Coast’s appearance in this year’s finals to an overwhelming percentage of football pundits, the Eagles have in all likelihood already sealed their spot.

That Essendon, a popular tip to at least be part of September again, and by enough observers to go deep into the finals series, is already all but out of the running.

And that of the good half-dozen teams currently outside by top eight on percentage only or by a game at most, that is, Collingwood, Melbourne, Port Adelaide, Fremantle, Gold Coast and the Western Bulldogs, only one, two at best, will be able to force their way in.

The 14th-placed Western Bulldogs after its nine-point win over Gold Coast. Photo: Getty

And that task may well be even harder given the presence of some latter-day finals regulars in GWS, Geelong and Sydney in the lower half of the eight.

Based on all the pre-season predictions, of the top eight incumbents it’s North Melbourne which would universally be regarded as the most vulnerable.

As inspiring as was the Roos’ win over Sydney on the SCG on Saturday night, they have a tough run coming up, Richmond this week, followed by GWS, Fremantle in Perth, Brisbane at home and Geelong away before their mid-season bye.

But on their SCG form, who would not at least give them a chance of grabbing three wins from that five-game block? That would leave North 7-5 headed into the break, needing probably to split the remaining 10 games at least 5-5 to become a finalist no-one, perhaps not even the Roos themselves, would dare have tipped.

Have a look at the list of the opponents North faces in those last 10 games, only three of whom are current top eight teams, and it’s a prospect far from fantasy.

In a round in which North produced the only upset, West Coast’s win was as emphatic as any team’s, particularly coming against a Port Adelaide outfit which was another popular pre-season fancy to date not living up to expectations.

North Melbourne have been the surprise-packet of 2018 so far, sitting in seventh place. Photo: Getty

There’s still not much fanfare about the Eagles outside Perth, and they, too have a challenging few weeks ahead – the Giants and Hawthorn away, and a Richmond still running rampant at home – but they’ve now won six on the trot, and the numbers aren’t lying.

Second on the ladder, West Coast is a different outfit altogether from that which limped into last season’s finals. Nic Naitanui’s return has made a big difference, but only as big as the new-found consistency of Jack Darling up forward, the emergence of Jack Redden on-ball, and the increasing impact of the exciting Willie Rioli.

But while the focus remains on the scoring potency, the 2018 Eagles are a much tougher proposition. Against Port Adelaide, a renowned hard-ball team, West Coast won the contested possession count on Saturday by a whopping 40.

The Eagles were ranked 15^th on the differentials for that stat last season. Currently, they’re in the top quarter.

Perhaps the starkest contrast on the ladder right now, funnily enough, is between the two winless teams at the bottom.

Carlton, racked by injuries it can’t afford, wasn’t terrible against Adelaide, but still ended up losing by 55 points. Brisbane, in the final game of the round, almost pulled off the upset of the season against Collingwood.

The Lions are stiff indeed to be 0-7, having been blown away just once this season, against Richmond, and having now lost three games by seven points or less. Chris Fagan’s team deserves a win, and if it can continue in Sunday’s vein, it will get one soon enough.

They, the Blues, St Kilda and probably the Bombers, however, can already starting planning for the longer term, with a couple more to join that list over the next few rounds.

Brisbane is proof enough of how tight this competition can be. But the “Round 7 rule” is also a handy reminder that if you don’t have enough wins on the board already, you’re probably not going to have enough come round 23, either.

Read more from Rohan Connolly, formerly a senior football writer for Fairfax, at Footyology, or watch Footyology TV here.