ADELAIDE'S defence was highlighted as its main vulnerability on the eve of season 2015, with most struggling to see any key position strength beyond full-back Daniel Talia.

The loss of Brent Reilly to a fractured skull compounded the retirement of Ben Rutten in 2014 and robbed the side of 432 games worth of defensive experience.

Talia and Brodie Smith began the year as the defence's most capped certain starters, with a combined 76 matches to their names.

However the Crows enter their round four clash against the Western Bulldogs boasting the AFL's stingiest backline in 2015.

They've conceded just 181 points so far this year and while three games is a tiny sample size, as coach Phil Walsh points out, the fact remains the Crows' back six have performed in 2015.

Small defender Luke Brown, who will play his 50th AFL game against the Bulldogs, singled out Kyle Hartigan for particular praise given he was subjected to the most external scrutiny of any in the club's back half before round one.

"It all starts with the kind of pressure our midfielders and forwards are applying – that makes it a lot easier," Brown said.

"We've played a few games together now over the last couple of years and we're starting to build good chemistry and we're communicating well.

"[Hartigan] would have taken a few people by surprise by how well he's going, but with the pre-season he's had and the things he was doing during the pre-season training drills it's no surprise for us.

"We know he can do that week in week out, so it's been good to see him perform at that level."

Since taking the reins from Michael Doughty at the start of 2013 as the club's premier small defender, Brown has become indispensible to the starting line up.

His quiet and unassuming nature is reflected by the way he approaches his football – there's no fuss or flash, just solid and reliable team play.

It's exactly what Walsh would desire.

The retirement of Doughty after the 2012 preliminary final loss to Hawthorn threw him into the deep end but having missed just one game since Brown has handled himself superbly.

He said his family would watch him notch his 50th game on Sunday afternoon.

"It's not something you really strive for when you start playing, you just want to play each week and help your team win, so it's a good little milestone," he said.

"Most of my friends, my parents will be watching this weekend.

"It's crept up pretty quickly but I've just been happy to keep playing my role."