TAKE THE top two key defenders out of any team in the AFL and most would struggle mightily.

Even high-flying Geelong didn't look quite the same without Matthew Scarlett and Harry Taylor anchoring the defence, but Carlton has quietly gone about its business without first-choice centre half-back Jarrad Waite and full-back Michael Jamison at the business end of the season.

Such losses would have been considered disastrous earlier on, but the Blues are headed toward their first finals series since 2001 having not conceded over 100 points to an opponent since the round 14 win over Fremantle.

Long considered the team's Achilles heel, the defensive unit has played a key role in Carlton's march back up the ladder with last week's effort against Port Adelaide a prime example, according to coach Brett Ratten.

Say what you like about the Power's wildly inconsistent form this year, but they have been home-turf bullies; winning eight of nine games at AAMI Stadium with an average score of 106 points before they met the Blues in round 20.

"I thought our back six was fantastic last week. I thought they stood up amazingly well because of the dominance of Port Adelaide at centre bounces," Ratten says.

"They gave us a real touch-up in the centre square there and a lot of the footy was thrust straight from centre bounces [inside 50] with six-on-six opportunities to score. I thought they did a great job for us."

Bret Thornton, who for so long was forced to play a lone hand in an undermanned defence, and emerging backman Paul Bower have taken on the bulk of the tall defensive assignments and haven't disappointed their coach.

"I think Thornton's season is one that's definitely been underrated throughout the competition," Ratten says.

"Paul Bower, coming back from his knee injury, has been fairly solid but his first half of the season was outstanding.

"I've been really pleased with those players to be able to take the next step in their development in leading other men and taking that responsibility on. I think it's been a great progression for them."

The pair has received plenty of support with Jordan Russell, Ryan Houlihan, Aaron Joseph, Dennis Armfield and Simon Wiggins all playing pivotal roles in recent weeks.

Walker, in particular, is one player Ratten is delighted to have back at full fitness after spending the first 17 weeks of the season nursing another right shoulder injury.

"We were licking our lips to see that run and dash from half-back [from him]," he says.

"He's 190cm, quick and can play anywhere. He really helps us back there."

Walker has played plenty of football as a defender in his 84 AFL games and he's not surprised at how well the back six has performed in the face of such adversity.

"It does almost become a side within a side," Walker says. "Defenders always seem to bond really well and everyone seems to know what they want out of each other.

"There's always a lot of constructive talk down there. Even when we might not be going too well the backline always sticks together.

"It really hurts to lose players of the quality of those two guys (Waite and Jamison), but I think it can only be a positive to look at how the team has played without them and know that they're going to come back in next year.

"I think it's something that we'll really be able to build on."