MOST tactical revolutions in AFL football begin with more of a whimper than a bang.

Fitzroy coach Robert Walls' famous kick-in huddle, North Melbourne's "Pagan's Paddock" and the scourge of attacking football, the flood, all began as a raising of the eyebrow from puzzled opponents.

They were gradually dissected by the strategists, before being revealed on a wider scale to a fascinated football public.

And such has been the case once again with the game's latest tactical ploy. Call it "Clarkson's cluster", call it, in a play on Walls's strategy of 25-odd years ago, the "muddle", but either way, it's an inherent plank of Hawthorn's raging success so far in 2008.

Opponents have torn their hair out trying to find a way through the Hawks' apparently impregnable midfield this season, their analysts working overtime and their videos on overdrive as they studied the brown-and-gold in action over and over again.

Finally, they found the secret. And it was Richmond coach Terry Wallace who lifted the lid on his coaching rival Alastair Clarkson's audacious strategy of employing a moveable, rolling defensive zone after the Tigers' narrow loss to the Hawks last Sunday.

Geelong cut a swathe through season 2007, literally, through the middle of the football ground. But it's space that, a year on, Hawthorn has repeatedly taken away from its opposition.

"We couldn't control the corridor like we've been able to control the corridor in other games, we couldn't get our play-ons going the same way as we've been able to get them going in other games," Wallace said. "Hawthorn has taken the game to another level, and that's a credit to their coaching staff. What they are doing is getting the game played on their terms week-in, week-out."

In basic terms, the Hawks force their opponents to play wide, taking the long route to goal. At an opposition kick-in, they'll form a central grid of up to 15 players, leaving the only free space along either defensive flank. There's nowhere else for the kicker to go.

And there the fun begins. If the kicker takes the obvious option, his team will be forced to hug the boundary or run into a wall of Hawthorn jumpers. If he switches direction, the Hawk zone simply slides across the ground in formation to block that space, too. Go back the other way again, and the Hawks go as well. It's intense defensive pressure, non-stop.

"As soon as you go wide, they rush in to hold you up," explains a rival club coach who has watched the Hawks intently.

"That's the first player's job, then he'll move around laterally on the mark so you've got to kick over him to go through the corridor.

"If you draw a line straight down the ground from the bloke manning the mark, they'll put a man 20 metres back from that, then another 40 metres back, and another 60 metres back. Inside of that, about 15-20 metres, there'll be another row of three or four, and then the same again getting towards the other side of the ground.

"But they won't go wider than the line on the edge of the centre square. Basically, they box up the whole corridor, allow you to go wider than that, and try to trap you into playing that wide football."

That generally means slower delivery into the forward line, which gives the Hawks a better chance of blocking up space near goal. Better still, so good is Clarkson's side's defensive pressure in the middle of the ground that the ball often doesn't get near goal at all.

The figures back it up. Hawthorn is conceding an average of only 42 inside-50s a game, the least of any side in the competition, five fewer than the next best team, St Kilda, and eight fewer than the AFL average. Last week, the Hawks allowed Richmond only 33 entries. And when they beat Fremantle in round two, by half-time, the Dockers had amassed 160-odd possessions for only 12 inside-50s.

Clarkson's team allows its opponents only 15 running bounces a game, the lowest in the AFL, four fewer than average. Its opponents have only 28%t of their midfield uncontested possessions within the corridor, again the lowest figure in the competition.

There's just no space in the middle of the ground when you play the Hawks, as North skipper and centreman Adam Simpson confirmed. "Definitely, when they do it the way they've been doing it," he said.

"We played them a few weeks ago and we handled it pretty well. I think we were in front for 90% of the game, so I wouldn't say it's unbreakable, but I would say it's pretty tight."

So the challenge is afoot. Will rivals follow the Hawks' lead? One senior coach thinks he saw signs of a similar strategy used by Port Adelaide in its win over St Kilda last week.

"I reckon it's going to be a bigger problem for teams than flooding was ever perceived to be," he said.

And just how will opponents break down the AFL's newest tactical innovation? By playing on at all costs, say rivals, refusing to give Hawthorn time to set its zone up.

It's a tough task, but achievable. And the considerable lure is the apparent fragility of the Hawks' defence once the midfield shield is penetrated.

While Richmond got inside there only 33 times last Sunday, it managed to score 15.4 when it did. In six games, opponents have scored on 56% of occasions they've entered the Hawks' defensive 50.

That's easily the worst figure of any side in the top eight. Over all 16 teams, only Port Adelaide, Melbourne and Fremantle allow more scores an entry than the Hawks.

"Once you get through the zone, they're actually pretty vulnerable," said the strategist. "Often, they'll be outnumbered in defence because they've all pushed up into the zone. The zone's been so effective that the ball doesn't actually get inside the 50, but when it does, they're in trouble."

That's partly why today's Hawthorn-Collingwood clash is being so eagerly awaited by clubs looking for some hope, not just because it features two of the more obvious challengers to Geelong's throne, but because it's the Magpies who appear to have the style best suited to taking on the Hawks.

Collingwood, unlike most of its rivals, doesn't mind taking the ball out wide on the path to goal. The Magpies also like to play on quickly, and prefer a kicking game to handball. They're three tendencies club strategists believe could bring the Hawks' rolling zone undone.

It's going to be a fascinating game within a game. But you're not going to hear the coaches admitting that on match eve. In fact, for Clarkson , it was a case of "what rolling zone?"

"It's a little bit mythical, to be honest," he said. "Teams have been working with zones from kick-ins to try to stop oppositions from sweeping the ball down the ground on a regular basis. We've done it reasonably effectively to date … sometimes that's been successful against some oppositions, and other times it hasn't."

His opposite number, Mick Malthouse, had the fire hose out, too. Nothing to see here. "I think Adelaide have had this game structure in place for four years (or) five years. Hawthorn have had it for several years, it hasn't just mysteriously appeared this year," he said.

"I don't think it's anything over-the-top radical, it's just the way they (Hawthorn) play."

Mind you, that could be news to Adelaide coach Neil Craig. "A lot of it can be (myth) because we experienced a bit of that ourselves in 2005 and 2006 in particular, where we read with interest numerous times the things we were doing but we had no idea we were doing," Craig said yesterday.

But that clearly ain't the case with the Hawks. The rolling zone, the cluster, the muddle is real. Hawthorn knows what it's doing, and now, so does everybody else. For a series of anxious prospective opponents, today may well present the first serious trial of an antidote. And you certainly sensed yesterday, that Malthouse and the Magpies were up for the challenge.

"It (the game) may well be on their terms and we might come away with a good going over and find out that we're not good enough under those sort of circumstances," he conceded.

"On the other side of the coin, it could well be that we play our style of game and make them change theirs."

If Collingwood doesn't, someone will. Most likely with another tactical innovation. One that, like Hawthorn's flavour of 2008, starts as a whisper, and ends, for frustrated opponents, with a loud, destructive bang.

Analysis

AFL football consists of several different games these days. There's the one played in the boardrooms, where clubs plan their futures, trying to ensure their financial security.

There's that more tiresome brand increasingly played out in the media by the media about the media.

And there's that other one, the sometimes seemingly incidental version featuring 16 teams, some of the best individual sporting talent in the land, some of the best football we're likely to see and some of the most intriguing battles of tactical wits we've witnessed.

The way this season is going, 2008 could be seen in hindsight as a fascinating watershed year in the continued evolution of AFL football.

Already, the incredible spiral in the numbers of interchanges affected by teams during the course of four quarters has forced practically every team in the same direction.

One hundred interchanges a side is becoming commonplace, virtually one a minute, so many that, as we witnessed in Sydney's controversial "19th man" case this week, it's easy for the poor old interchange steward to lose count.

There's the teams that boast the big key forwards, Lance Franklin and Jarryd Roughead for Hawthorn, Jonathan Brown and Daniel Bradshaw for the Brisbane Lions, Brendan Fevola for Carlton.

After being prematurely condemned to the scrapheap, the Western Bulldogs' multi-pronged goalkicking spread is back in favour, no huge marking targets to speak of (save a pinch-hitting ruckman in Will Minson) but a wide array of potential scorers making the Bulldogs easily the AFL's heaviest scoring team. That's before you even start talking about the rolling zone employed by Hawthorn that, according to many learned coaching types at rival clubs, has the potential to have a far more wide-reaching impact on the game than the well-documented defensive flood ever has.

Only a couple of years ago, many doomsayers were dismissing the game as an overly negative and unattractive slugfest or an overly sanitised, non-contact version of keepings-off. Now, AFL football seems to be encompassing a greater divergence of approaches and contrasting styles than ever.

We still talk about the huddle, more than a quarter of a century after Robert Walls taught his Fitzroy charges how to virtually guarantee possession from a kick-in. The clearing out of an entire forward line for the champion qualities of a key forward called Wayne Carey and a host of eager crumbers feeding off his brilliance not only earned Denis Pagan a couple of premierships, but a style of football named after him.

The flood still has currency well over a decade after Rodney Eade's Sydney used it to such effect, while the latter version of the Swans under Paul Roos have made contested football their own.

Alastair Clarkson could well end up with a significant turn in football's direction named after him, too. Or maybe, by season's end, he and the Hawks' rolling zone will have been trumped by another bolder tactic.

It's certainly already proving one of the most fascinating football seasons we've been privileged to witness. If only those giant-sized egos could tear themselves away from the mirror and take a look.