MOST teams who have taken on Hawthorn this season have had some serious homework to do beforehand. And that will have been no different for Geelong before tonight's MCG blockbuster.

The Hawks' much-discussed rolling defensive zone, which forces opponents short and wide, needs smart thinking to counter it, even when that opponent is the rampant force the Cats are at the moment.

Geelong coach Mark Thompson said as much on Wednesday when he acknowledged how effective "Clarkson's cluster" had been. But there was an important qualifier: "The way we play gives us a chance to actually break through it," he said. He was spot-on. On several fronts.

Only three sides have beaten Hawthorn this year — the Western Bulldogs, North Melbourne and, last week, St Kilda. All those defeats have come in the past seven games as the Hawks have gradually come back to the field, the suspicion being that the opposition is beginning to work them out.

Quick movement of the football and plenty of handball to penetrate the Hawthorn zone have been key elements of those results. And Geelong is a master of both, the speed of its play at times breathtaking, and its handball prolific, the Cats averaging nearly 200 handballs a game, about 30 more than the nearest rival. No one hits the short target quite like Geelong.

But those starting to find chinks in the Hawthorn armour might also have discovered another Achilles heel as well, one that isn't related directly to another talking point, the alleged vulnerability of its defence.

In fact, it has as much to do with what, ironically, has clearly been a strength of the Hawks. The effectiveness of their kicking.

Hawthorn won't tolerate poor kicking, either in its potential recruits or those already on the list who hope to play senior football consistently.

That thinking reflects in a disposal efficiency this season of 78%, the best in the AFL.

The Hawks also average the fewest ineffective kicks and second-fewest clanger kicks in the competition.

But the obsession with hitting targets comes at a cost, one that is becoming more pronounced as the season goes on. When the heat is put on the Hawks, their determination still to dispose of the ball to clear advantage is seeing them caught all too often.

In 16 games this year, Hawthorn has been "pinged" for holding the ball on 94 occasions, a whopping 25 times more than the next-highest figure, and an average of nearly six a game.

The figure reached as much as nine in the Hawks' first loss of the season, to the Bulldogs at Aurora Stadium in round 10. That afternoon, as the Bulldogs combined quick run and skilful use of the football with fierce defensive pressure, what disposals the Hawks were able to get away were far less polished than usual, their return of 75% their worst return in any game this season.

Like the Bulldogs, North Melbourne, in Hawthorn's second loss of the season, also moved the ball quickly by hand to break the cluster. And similarly, the Roos also exerted plenty of defensive pressure.

Hawthorn ended up hitting the target by foot with only 66% of its kicks, its worst result in 2008.

The Hawks have the second-lowest kick-to-handball ratio behind Geelong, which should make for plenty of disposals this evening. But if the Cats are able to close down their handball options, their hesitancy to kick to contests could leave them vulnerable.

While Hawthorn is second in the AFL for handball receives, it's also equal-last for blocks. The Hawks don't provide much protection for their ball-carrier, not so much a comment on a lack of defensive responsibility as on the usual surety of their disposal, and on another effect of the cluster.

The rolling zone, formed as a grid, has players guarding space rather than opponents. It means that when a Hawthorn player wins the ball from a turnover, particularly in defence, he'll have a line of teammates across the ground free to support him.

Theoretically, anyway. Opponents have begun to start manning up those loose players, with, for the Hawks, worrying results. "They want to take it a certain way, laterally," says an opposition strategist. "When they come out of defence on the turnover, blokes like (Brent) Guerra and (Grant) Birchall will have spread out 30-40 metres wide of the contest, and they spread the ball wide to them, just like from a rugby scrum.

"If you can stop them doing that, they'll tend to stop and prop a bit with the ball. Their way is blocked, so they hang on a bit more trying to hit a target." And, as the figures show, can get pounced upon as a result.

It all raises a legitimate question. Do the Hawks have enough of a plan B?

Hawthorn's brand of football has been tested already in 2008. But tonight's is the exam it simply can't afford to fail, tactically as well as on the scoreboard.