While Giants coach Adam Kingsley spoke of his side's reduced scoring after the weekend's loss to Adelaide, they have also conceded 102 and 94 in the last two games.
Idun and the rest of the GWS defence must lift at home on Saturday night, given the potency of Carlton's attack and the twin threat posed by the Blues' key forwards Charlie Curnow and Harry McKay.
"It's definitely not something we're happy about, conceding so many points," Idun said.
"We're not keeping our backyard clean at the moment in terms of scrapping life-and-death, winning our contests, things like that.
"If you're not defending properly, offence suffers on the back of that."
Asked about the opportunity to turn their defensive work around, Idun said: "No better chance, against probably the best forward line in the comp - and especially the two best keys (forwards) in the comp.
"We're going to take this battle pretty personally and we need a response from what we did last week.
"We're playing a bit too much one-on-one, we need to come off and support each other in the air."
Idun can play tall or small, meaning he could go to any of the Carlton forwards during the game as needed.
He's a self-described footy head who usually watches five games a weekend, so he knows what is coming.
"I like to study every forward and that's important as well, because we want to be a system defence," he said.
"I might spend a few minutes on every player ... in terms of supporting each other, that's also important.
"It's scary to see how much momentum (Carlton) can get pretty quickly.
"They're a juggernaut of a team and there's no better way, to respond against a team like that.
"I pride myself on being able to play on any type of forward."
The upset loss to the Crows put GWS out of the top eight and Idun said the Giants aren't sticking to what they know works.
"Our Tsunami, as we like to call it, is defensive and offensive," he said.
"If our pressure falls off, our offence goes with that.
"We need to get better in dealing with opposition momentum. Other teams are getting run-ons way too frequently.
"Adelaide scored seven goals in a row, which is embarrassing, really.
"We need to keep working on that, screw our guts up and start winning the contest."
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