Ground: ES Etihad Stadium, Docklands, Melbourne; MCG Melbourne Cricket Ground; SS Simonds Stadium, Geelong; ANZ ANZ Stadium, Sydney; SCG Sydney Cricket Ground; SKS Skoda Stadium, Sydney; PS Patersons Stadium, Perth.

Ground: ES Etihad Stadium, Docklands, Melbourne; MCG Melbourne Cricket Ground; SS Simonds Stadium, Geelong; ANZ ANZ Stadium, Sydney; SCG Sydney Cricket Ground; SKS Skoda Stadium, Sydney; PS Patersons Stadium, Perth.

There's a lot of statistics in AFL football, but as far as this season's premiership is concerned, and for Sydney and Fremantle in particular, there's one with far more significance than any other.

To say you can't win the flag without finishing top four in the modern era isn't just a truism, it's an incontrovertible fact, and if you need some numbers to back it up, try these on for size.

Since the revamp of the final eight in 2000, we've had 52 teams play in a preliminary final for the right to earn a crack at the ultimate prize. No fewer than 50 of those have finished the regular season with the double chance, the two exceptions Hawthorn in 2001, and Collingwood in 2007, neither of which was able make it any further.

Celebration: Sydney Swans fans celebrate winning last year's grand final.

Celebration: Sydney Swans fans celebrate winning last year's grand final but the weight of history and statistics are against a repeat. Photo: Getty Images

If you want to put it another way, based on history, those teams that finish between fifth and eighth after round 23 have about a 4 per cent chance of making it to preliminary final weekend, and will have to create history to appear on the grand final stage, let alone win one.

Which means that while there's another battle going on in the bottom half of the eight, and while Richmond remain a theoretical chance of a top-four spot, with Collingwood a longshot, it's the Swans and Dockers who in premiership terms, are fighting their own elimination final over the course of the next six games. And the indications are it's going to be tight.

You might not think so glancing at the ladder, with the Swans in fourth spot, one game and more than 20 percentage points ahead of Fremantle. But that's not taking into account the draws of the sides.

Sydney have two games they should win comfortably, against Western Bulldogs and St Kilda, two testing assignments in which they will at least start favourites, against Richmond and Collingwood, and a final couple, against Hawthorn and Geelong, in which they almost certainly won't, one of which there's every chance they will need to jag to hang on to the double chance.

Fremantle, in contrast, have the smoothest run to the finals of any side in the eight, playing just one top-eight rival, and the three bottom sides. The Dockers take on Adelaide at home this week, and have other challenges in Carlton at Etihad Stadium and Port Adelaide, but also a terrific chance to close the percentage gap on the Swans with games against Greater Western Sydney, Melbourne and St Kilda.

Sydney arguably have better form than any top-order rivals, but they will need to carry it right through to the round-22 clash with Hawthorn at ANZ Stadium and the toughest last game possible, Geelong at Simonds Stadium, where the Cats have won 39 of their past 40 games.

The Swans upset the Hawks when it mattered most last year, and were the victors in that one home game Geelong didn't win. But those two sides are also responsible for two of Sydney's three losses this season. Neither will Sydney be resting easy even if they manage to cause one upset in that final fortnight of the season.

Whichever of Fremantle and Sydney misses out on the top four will be one of the better-qualified sides we've seen take the sudden-death finals route.