IF ST Paul's epiphany was a vision of Christ on the road to Damascus, Brett Ratten only needed to glance at the MCG scoreboard in the Carlton-Essendon game in round three to see the light.

The score read: Carlton 134, Essendon 150. The Blues managed to lose despite eight goals from Brendan Fevola, Chris Judd's 32 touches, nine clearances and two goals, Nick Stevens sending the ball inside 50 metres 10 times, a strong game from Marc Murphy and a startling debut from No. 1 draft pick Matthew Kreuzer.

The Blues were defensively incompetent. That they had lost a shoot-out in which they had perhaps five of the best six or seven players on the ground prompted Ratten to re-think his approach.

His subsequent conversion to a more defensive method has been the salvation of the Blues and should Ratten go on to a distinguished coaching career, there's a fair chance round 3, 2008, will be remembered as the loss that saved him.

Would the Blues have embraced defence so unequivocally had they won that night? Carlton insiders think probably not. In essence, Ratten asked himself the same question St Paul posed to Christ: "Where are you going?"

A new game style was developed immediately after round three. Numbers were dropped back on occasion to protect an inexperienced backline.

Tempo footy — the unsightly bane of the modern supporter — was deployed to stop the opposition's flow of goals. Judd spent most of the last quarter of the round four game against Collingwood playing as a defensive sweeper from half-back.

Carlton of rounds 1-3 leaked an average of 130 points, and had conceded 100 points or more in 24 consecutive games.

Teams that do that are condemned to burn in the ladder's lower reaches. The Blues, lest we forget, had lost 14 games on the trot before the rebirth against Collingwood.

From rounds four to 12, Carlton's average points against was 92 — an improvement of better than six goals a game. Since Ratten's conversion, only three teams have broken the 100-point barrier against the Blues (the Lions, Geelong, Adelaide), and they're the only teams to have beaten Carlton over that period.

Carlton's strength — its midfield — now protects a defence that, left to its own devices, would still have holes punched through it.

Whereas round three was a catalyst for a complete reappraisal by the Carlton match committee, Essendon's win that night arguably has not helped its cause.

Matthew Knights persisted with his highly attacking game style, and the Bombers won only one of the subsequent nine games; while Ratten tightened up, Knights has, until recently, paid little heed to restricting the opposition.

Post-round three, Essendon has conceded an average of 123 points a game, having given up 115 a game for the more encouraging first three matches.

For the Bombers, the season nadir was surely reached in the first half of the "Dreamtime at the G," when the Tigers — who aren't going to worry Geelong — scored the first eight goals; to that point, Essendon had given up 21 consecutive goals (it had conceded the last 13 against the Swans).

The following Friday night, Essendon scrapped it out with a profligate Adelaide and, aided by the home team's inaccuracy and a wet ball, nearly got over the line. The Bombers seemed more than vaguely aware of defensive responsibilities that evening, and weren't hurtling downhill on one ski.

When the losing habit was finally broken against West Coast last Friday, the Dons contained the Eagles to 13.13 (91) — belated brakes were being applied.

In fairness to Knights, instead of Judd, Murphy and Stevens, the Dons have Mark McVeigh and a string of B and C-grade midfielders. Take McVeigh out and there's no obvious player worth tagging (Andy Lovett isn't a bona fide midfielder). They have Dustin Fletcher and Paddy Ryder down back, though.

Knights has contended that his concentration on attack is just a phase and that, as his young team develops harder bodies and minds, the switch will be flicked to a more accountable style. Maybe that process is underway.

The notion that a coach must stay the course, even with a flawed game plan, is nonsense. Paul Roos didn't open up with what became Sydney's boa constrictions; it took until 2005 for that defence-first style to be bedded down. Malcolm Blight couldn't quite land a flag with all-out attack at Geelong, and his Adelaide premiership teams were defensively adept.

Ratten's Blues will see to it that Essendon won't score 150 points again on Sunday. What Essendon gives up will be a measure of how much Knights is willing to concede, in every sense.