Umpire Matt Stevic could never have known when he blew his whistle in the final minute of that first qualifying final on September 4 that what he was really doing was sounding the death knell for Geelong's four-year dynasty. 

For in those dying seconds, when Cameron Ling's kick from 40 metres skidded through the goals at the city end, the Cats looked to have scored the most improbable of wins over St Kilda. But in the hurly-burly of the preceding passage of play, in which the ball was squeezed out to Ling, Stevic had seen Cameron Mooney pile-drive Saint James Gwilt into the MCG turf. 

He blew his whistle and signalled a free-kick to Gwilt. The goal was disallowed. Ling's joy turned to despair. Geelong fans put their hands to their heads. Mooney began mouthing off at Stevic telling him he'd cost the Cats the game. Up in the coaches box, Cats coach Mark Thompson was absolutely filthy, for he knew the consequences of a loss. It meant a preliminary final match-up, in all likelihood, with Collingwood. 

If Stevic had turned a blind eye to Mooney's careless tackle - and there are plenty of umpires, in the helter-skelter moments of the last quarter of a final, who would have done exactly that - then Geelong would have won through to a preliminary final against the Bulldogs. They would have gone into that match after a week's break, probably won - and then, who knows, maybe even given the grand final a shake. 

As it was, the Cats' bubble had been pricked and their mortality revealed. Thompson's Invincibles hobbled into a preliminary final, where they were resoundingly belted by the Magpies.

So Stevic's whistle - which signalled a correct decision, incidentally - has set off a chain of events that few could have foreseen. The whole Geelong edifice since that moment has begun shaking, and losing bricks, as if struck by an earthquake. 

First, Gary Ablett, the club's best player, decided to leave. He was followed out the door by the coach, who cited burnout. The president Frank Costa - who, with CEO Brian Cook has transformed the club - is on the way out. And today, assistant coach Brendan McCartney packed up his kitbag and announced he was heading to Essendon. 

How's that for upheaval in the space of three weeks? Suddenly the most successful club in the comp these past four seasons has developed a slight whiff about it. 

McCartney, who had been a member of the Cats coaching panel since 2000, was also development academy director and, in a media release today, Geelong' football operations manager Neil Balme could not hide his disappointment at the news of his exit.

"It was in the club's plans for Brendan to become a development coach who would solely focus on developing our younger players however he has now informed us he is looking to pursue a senior match day role instead," Balme said. "On this basis we have reluctantly accepted Brendan's decision to resign."

Some of the turmoil the Cats have brought on themselves. On the final day of trade week, they lost highly-rated youngster Jeremy Laidler to Carlton after deciding to renew Darren Milburn's contract. Laidler, a defender, is a natural replacement for Milburn. 

Milburn is 33, and looked terribly slow in the loss to Collingwood, as though the game had passed him by (an observation that could also be made of one or two teammates, it has to be said.) 

So at a time when a harsh call needed to be made on Milburn, the club wimped it - and in trying to hang on to faded glories, it lost a player of the future. Laidler said he knew he would get a start at Carlton.

In the modern game, the line between success and failure can be as thin as a gossamer thread. In the same way, the difference between a dynasty and very successful four-year era can be shaped by nothing more substantial than the tweet of an umpires' whistle.