Carlton key-position player Lachie Henderson says confidence is steadily building among the Blues' inexperienced but in-form AFL defensive unit.

The 21-year-old former forward has had jobs on some of the AFL's biggest stars since being shifted to defence after first-choice fullback Michael Jamison went down with a knee injury in round 14.

Even when Jamison made his return, against Hawthorn in round 22, Henderson was stationed on Hawks superstar Lance Franklin.

And he was handed the job on Essendon's talented young forward Michael Hurley in Sunday's elimination final win.

While Hurley looked dangerous early, prompting the Blues to switch Jamison onto him late in the first term, Henderson ended up having one of the best games of his budding 48-match career.

He took seven marks in defence, six of which came from Essendon kicks.

Despite having also had the odd difficult day on the likes of the Western Bulldogs' Barry Hall and Collingwood's Travis Cloke early in his shift fo defence, Henderson said he was relishing the role.

"The switch down back's been good. Jamo went down early in the year and I went back there and I've just grown in confidence from that, which is nice," Henderson said.

"It's just good to be playing footy and the defence itself is going really well, with the young group we've got down there."

While Henderson is the newest member of Carlton's backline, most of the defenders who lined up against the Bombers on Sunday were not there last year, a tribute to the Blues' coaching staff.

Recruits Nick Duigan and Jeremy Laidler have become integral components, while Chris Yarran's conversion from goalsneak to creative backman has been a revelation.

It has helped the Blues shave an average 13 points per game conceded this season, the second-biggest improvement of any club.

Only Saturday night's semi-final opponents West Coast, who have cut their opposition's average scores by a remarkable 27 points while rising from the wooden spoon to the top four, have made a bigger defensive gain.

Henderson said the Blues' first finals win in a decade provided a huge boost.

But he acknowledged the clash with an Eagles side, who kicked the biggest score Carlton have conceded all year in round 14 and who have won their past 10 matches at Patersons Stadium, was more daunting.

"Any away trip is always tough," Henderson said.

"They're playing some ripping footy and we'll need to play our best footy to really take it up to them."

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