Undermanned and underestimated, Essendon pulled off the shock defeat of the season tonight when it knocked off the previously unbeaten Geelong by four points at Etihad Stadium.

In a performance which few could have foreseen - certainly not the punter who placed $1million on the Cats to win at the skinny odds of $1.09 - the Bombers rediscovered their mojo from earlier in the season, employing the forward press with gusto, tackling with a manic fervour, swarming around the ball and completely throwing the Cats out of their stride.

The win ended a five-match run of defeats, which had threatened to scupper the Bombers' season, and begged the question: where was this Essendon spirit against Hawthorn last week, or North Melbourne the week before, or Fremantle, Melbourne and Port Adelaide? It was as if a transformation had come over the side, ahead of this much-hyped game that pitted their assistant coach Mark Thompson against the club he coached to two premierships - until his shock departure last year.

Geelong kicked the first three goals of the game and looked to be headed for the comfortable victory that many had predicted. But then, without warning, Essendon kicked its first through Dyson Heppell, then another to Angus Monfries and, by quarter time, had hit the front, 4.3-27 to 3.3-21. It was a lead they were to hold for the rest of the match, stretching it out to 33 points at one point in the third quarter.

But just when they looked to have the match in the bag, back came Geelong. And the fightback was led by Steve Johnson, hitherto unsighted, who kicked three goals in the last term, the second of them while lying on his back in the goalsquare and somehow having the presence of mind to jam the ball on to his boot.

That brought the Cats to within 10 points, with five minutes remaining. And when Mitch Duncan slotted a set shot from 35 metres, the margin was four points and it looked as though Geelong was going to conjure one of the great Houdini escapes in recent memory.

But a steadier from Jake Melksham, who banged one through from the goalsquare, gave the Bombers the breathing space they needed - and a truly memorable win. The sort of win that can revive a season.

Paddy Ryder played an inspired game after being roundly criticised for his lacklustre displays in recent weeks, while Heath Hocking was a pillar of strength in the midfield, racking up 25 possessions and 13 tackles. Dyson Heppell, Melksham and Ben Howlett were among the other young Bombers who helped deliver the club a much-needed win, and coach James Hird a reprieve.

The Cats missed Joel Selwood's toughness in the midfield, and the grunt of Joel Corey, who was a late withdrawal. But they could never complain about their injury list because the Bombers were without many of their best, including skipper Jobe Watson, and their starting centre-square line-up was very much their B-grade midfield.

Many of the young Cats failed to fire. Allen Christenson might have been best afield against Adelaide in the comfortbale confines of Skilled Stadium last week, but he was invisible tonight. Pretty much the same with Daniel Menzel and Nathan Vardy.

Both Thompson, and another Geelong defector in the Essendon box, Brendan McCartney, used their intimate knowledge of the Geelong players to good advantage. Andrew Welsh started on Matthew Scarlett and totally curbed his influence, while Jimmy Bartel and Brad Ottens were also well below their best.

The Cats' forward line again lacked sparkle and if there's one area that will concern coach Chris Scott, and his assistants, in the lead-up to September, it is the sometimes flaky nature of its attack and how - compared to Collingwood and Hawthorn, in particular - they can struggle without any dominant marking forwards. James Podsiadly went goalless, as did Menzel and Bartel.

But coach Scott can concole himself with the knowledge that no coach in VFL/AFL history has made such a successful start to their career - 14 straight wins.

James Hird, meanwhile, walked down from the coach's box with a million-dollar smile. The same could not be said of our punter friend who will be cursing Hird and his hot-and-cold Bombers for a very long time.