Size isn't everything, so I've heard, it's what you do with it that counts. Fortunately for both Essendon and West Coast right now, neither size, nor putting it to good use, is proving much of an issue. Watching the two most improved sides in the AFL slug it out at Etihad Stadium on Sunday it was hard not to draw the conclusion that the game's evolution has thrown up another of its natural mutations.

In the last few years alone, the game has developed at breakneck speed to combat rolling zones, Geelong handballing through the corridor, Saints Footy and now the ubiquitous forward press that has served Collingwood with such distinction. Constant adaptability is one of the game's great strengths and the latest variance appears to satisfy traditionalist cravings and once again place a premium on height and winning contested marks.

The forward press and ultra-aggressive tackle pressure mastered by the ‘Pies and now imitated by almost all their rivals is a given. However, both Essendon and West Coast have modified their games to take advantage of their tall, mobile lists.

The question is: is this the formula that will challenge Collingwood's dominance of the competition?

It has become assumed that to compete alongside Mick Malthouse's juggernaut their opposition is compelled to adopt certain positions and strategies.

Small forwards, operating primarily defensively, is one such development that Carlton, and Eddie Betts in particular, are employing to some success. Another is the use of the flanks to retain possession in the hands of mobile wingmen, rather than kicking to a low-percentage contest and risk a turnover - a weapon Chris Scott has added to Geelong's considerable arsenal. Perhaps the most obvious, and talked about, is the now almost universal use of a pinch-hitting second ruckman who can rest forward (or back, in Leigh Brown's case).

While the Bombers and Eagles have incorporated most of these developments, they have done so without compromising the natural height advantages offered by their lists and in the process introduced an early prototype for beating the very system they are aping.

By utilising mobile talls of the likes of Michael Hurley, Paddy Ryder and Tom Bellchambers, Essendon has been able to set the tempo demanded by James Hird, without sacrificing any physical presence or marking ability. This means their attacking structure remains primed to compete for contested marks and burst packs, an essential dimension to competing against sides, like Collingwood, employing at least one spare defender.

For the opening half against the Bombers on Sunday, the Eagles also showed that by cultivating such a forest of tall timber they could harvest other benefits. One notable payback was West Coast's constant contested mark threat throughout the ground. With Dean Cox, Nic Naitanui, Quinten Lynch, Josh Kennedy, and others, able to provide a range of targets, the Eagles were able to launch zone-busting kicks out of defence, bypassing the forward press, with the same gang able to also honour midfielders looking for an ‘anywhere' inside-50 disposal.

Hird and John Worsfold clearly deserve credit for turning around the fortunes of their sides in the off-season and adapting to how modern footy is being played. The inability of sides as capable as St Kilda, the Bulldogs and even Hawthorn to operate in this changed landscape shows it cannot have been easy. Whether by luck or design, both have managed (or chosen) to bring their playing styles in line with fashion with the inclusion of a few extra feet and inches.

Both have also benefited from the newly introduced substitute rule. The combinations of Cox and Naitanui, and Hille (or Bellchambers) and Ryder fit this new model perfectly with each equally adept in the centre or the forward line. All are also totally committed to the increasingly demanding desperation required at ground level to survive in the modern hothouse environment.

This was typified early in the third quarter of Sunday's game, just as the balance was tipping Essendon's way. David Hille, all 201cm and 108kg of him flung himself out of a contest like an old-fashioned rugby union scrumhalf, delivering a perfect diving handball that ultimately led to Kyle Reimers notching a critical goal.

If all of this sounds like the pudding is being over-egged for two sides that, after round 24, are still likely to finish nearer the middle than the top of the ladder, fear not Collingwood fans. Despite the optimism for both the Bombers and the Eagles, they are still playing catch-up at the forward press to the team that already has it mastered, they are imitating the swing-hitting ruck combination already employed to flag-winning success by the Magpies and in Travis Cloke and Chris Dawes, Mick Malthouse has at his disposal two of the best contested marks in the competition in his forward line and in Heath Shaw and Ben Reid, two of the best overhead down the back.

Essendon proved on ANZAC Day that by reaching for the sky they could compete with the all-conquering premiers. This was perhaps the first glimpse of a trend that could lead to a systematic shift in how sides are set-up, with the express aim of challenging the dominant side.

I'm not sure I'd be too concerned yet if I was part of the ‘Buckhouse' brains trust, but round seven could be worth revisiting as a key juncture in the destination of this or (more probably) next season's flag.