A stunning second half by Essendon has delivered Carlton their biggest defeat of the season and left the Bombers looking the more likely AFL finalists.

Essendon overcame the loss of star midfielder Jobe Watson midway through the second term to storm back from a 14-point deficit late in the opening half and trounce the Blues 21.10 (136) to 9.13 (67) in front of 83,407 people at the MCG.

While it was the Bombers' fifth straight win over their fierce rivals, the 69-point margin was by far the most emphatic result of that streak and also easily the Blues' biggest loss this year.

With both sides having entered the game on 6-6 records, the Bombers shored up their top eight berth, while Carlton are looking tottery, having managed just four wins from the past 11 rounds, after opening the season with two straight victories.

Incredibly, after looking in trouble, when 14 points down deep in the second term, they outscored the Blues 16.6 (102) to 2.7 (19) for the rest of the game.

It was even more stunning, given Watson was clearly their best player before limping from the ground midway through the second term and not returning.

Carlton kicked three quick goals after he went off, but the Bombers turned the tide in the final minutes of the first half to nose ahead by four points at the long break.

They then completely dominated the third quarter, outscoring Carlton 6.4 to 1.2 to take a commanding six-goal lead at the last change.

Midfielder Andrew Welsh was superb for the Bombers.

Assigned to Carlton skipper Chris Judd, he not only kept the brilliant Blue from having a major impact, but gathered nine touches himself for the third quarter to get things moving his side's way.

Fellow midfielder Brent Stanton stepped up after a quiet first half to help make up for Watson's absence, while midfield speedster Andy Lovett also lit up his side after halftime.

The Bombers, who tackled ferociously, were also able to apply the pressure at both ends of the ground.

Young key defender Tayte Pears, playing on Blues spearhead Brendan Fevola, kept the Carlton star to two goals and also managed to twice run off him to set up consecutive goals early in the third quarter.

With the Bombers' confidence soaring heading into the final quarter, they turned the game into a team highlights reel.

Lovett led the way with a sensational high-leaping mark over Carlton ruckman Shaun Hampson on the wing then followed it up with back-to-back goals before Scott Lucas and Paddy Ryder joined the party soon after.

Angus Monfries finished with five goals for the Bombers, while goalsneak Eddie Betts snared three for the Blues.

Essendon coach Matthew Knights said it was his side's best four-quarter performance of the season, particularly after losing Watson.

The extent of the damage to Watson's ankle was unknown, but worryingly Knights said he had lost feeling in the bottom part of his leg.

"We spoke at halftime that it would be a magnificent victory if we could come away with a win, only having 21 players," Knights said.

He said the experience of a finals-like atmosphere would be "invaluable" for his young side, but also said they needed to come back to earth quickly ahead of another huge clash against Collingwood next Friday night.

Carlton coach Brett Ratten had no doubt it was his team's worst performance of the year and lamented their large number of disposal errors.

"That probably burst our bubble a little bit in the first half, but gee, the fight in the third quarter was pretty embarassing, I think," Ratten said.

He said the big test now was how his players bounced back from such a poor showing.

The Blues also had an injury worry, with defender Paul Bower to have scans after hurting his knee late in the third term.

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