CLARKSON'S Cluster, or whatever you might call the rolling, defensive zone Hawthorn has employed with brilliant effect in 2008, has rightly been praised for its innovative qualities.

But it is the way of professional football that teams are already scheming and planning to break down the method devised by Hawthorn coach Alastair Clarkson. At the MCG yesterday, North Melbourne punched holes in it at crucial stages and seized an upset victory.

The weakness in the zone is at the back. Twice in the opening minutes of the final quarter, with the game on the line, North Melbourne forward Lindsay Thomas was allowed to take possession within 30 metres of goal without a semblance of a Hawthorn defender in his shadow, for at the time, the Hawks were guarding space. Thomas needs no such invitation; he drilled both goals.

Slotting a third in the space of nine minutes a moment or two later, the South Australian Thomas became the game-breaker. Coach Dean Laidley said the 20-year-old had shown grit from the time he moved from country South Australia to play with Port Adelaide in the SANFL. "The background of this kid is he's a wonderful story. He shifted up from Port Lincoln with seven or eight of his teammates. I think all of them went back except for Lindsay. He hung on. He's gone on to play some terrific footy. From when he walked in to the club, he wouldn't look anyone in the eye; now he's just improved and matured," Laidley said.

Of course, the zone is not easily broken, as Hawthorn's record suggests. It requires quick ball movement and handball, and North Melbourne was clearly instructed to run and carry the football yesterday. "That's the only way you can break down their zone, because they do it so well," said Daniel Harris, the North midfielder. "If you just kick it down the line, it plays straight into their hands. You have to handball and get it on quickly and catch them out."

Asked if teams were beginning to unravel Clarkson's riddles, Harris pointed out the Hawks' healthy ladder position. But pushed further, he said: "There's definitely space at the back. They pretty much tell you: 'If you're good enough to get it out the back and through us, it'll open up'."

This was a groundbreaking day for North, both tactically and in more basic terms. Laidley had thought his team "out-and-out soft" against Fremantle in Perth last weekend, and anticipated a reaction. "I knew they'd play well today, after last week," said the coach.

It was evident from the start in the actions of players such as Harris, who was used as a stormtrooper off the bench. Harris had more than 30 disposals and his dozen contested balls was easily the best on the field. It had been a focus, for Laidley had given him some verbal stick in Perth, a rumour confirmed by Harris yesterday.

"For every reason, too," he said. "I think across the board it wasn't acceptable and I was part of that. That's footy. You cop a spray, you move on."

Harris said the Roos were ready. "Internally in the club, we knew if we play as a unit, do the team things, we're always a show. We've got a good record against Hawthorn. You have to win the contested footy and that was the focus.

"A team like that, they'll slice you with their skills. Basically, everyone has to put pressure on, second man in, second man in and they'll cough it up. The turnovers led to goals which is what we wanted.

"It gets back to winning your own footy, winning contested football and getting it into your forwards as quickly as possible. We've got (Nathan) Thompson, (Shannon) Grant and (Corey) Jones up there and also Lindsay and 'Mattie' Campbell who can kick a winning score for us. We've got to get it in there quick, get it over that zone they make."

When the siren blared out, Harris had the football in the middle, and was pile-driven into the turf by three Hawthorn players. But he lived to laugh it off. The enmity between the teams is strong, particularly after the previous encounter. "There was a fair bit said out there, but it comes back to your actions, winning the footy," he said. "That's being tough, putting your head over the footy. We don't think running around belting blokes is tough."