CALL THEM the patchwork quilt Blues.

They are list manager Stephen Silvagni's assortment of recycled talent and bargain draft picks helping form the AFL's most underrated backline.

Second-year Carlton coach Brendon Bolton, with Silvagni's assistance, made constructing a sturdy defence the first task in his Blue-print.

The foundations are built around Sydney rookie discard Sam Rowe, who was plucked from the football wilderness by Carlton in 2011 as a 24-year-old from SANFL club Norwood.

This one-time spare-parts key-position player now mans the opposition's No.1 tall forward each week.

Rowe’s formline is outstanding, conceding only 11 goals in seven games this year. Not bad considering he’s locked horns with some of the competition's biggest names – Jack Riewoldt, Jesse Hogan, Joe Daniher, Tom Lynch, Charlie Dixon, Lance Franklin and Darcy Moore.

Veteran Kade Simpson, like Rowe, is still defying his draft history; the No.45 pick in the 2002 NAB AFL Draft remains an integral member of the defence.

Reigning best and fairest Sam Docherty, nabbed from the Lions in exchange for draft selection 33 in 2013, is the Blues’ other running linchpin.

Among Docherty’s backline buddies are fellow second-club players Caleb Marchbank, Lachie Plowman and Alex Silvagni. Plowman arrived at Carlton in a deal in which it parted with a series of picks, including No.17 in last year's draft, but Marchbank was unproven at the elite level and Silvagni is a dual rookie draft selection.

Rounding out the defensive rotation are Simon White and mid-range 2016 draftees Harrison Macreadie and Tom Williamson.

Despite their collective low-key entries to Ikon Park, this motley bunch are starting to catch the footy world’s attention.

"(Defence) is a real strength of theirs, mainly with Docherty and Simpson," an opposition analyst told AFL.com.au.

"But they also have good younger guys, like Marchbank and Plowman. They have more talent than they are given credit for."

The Blues' philosophy is that the whole is greater than the sum of its parts, with Bolton crediting Docherty, Simpson and, more recently, Plowman for keeping it all together.

"Often the plays you see us cut off are a result of organisation, in terms of another player organising someone else," Bolton said.

"We often just see the player involved in it on the screen, but the instruction off the ball is the most critical."

Carlton is second in the AFL in defensive-50 intercept marks and fourth in intercepts and defensive-50 marks, and has conceded the eighth-fewest points.

Opposition sides score off just 45.2 per cent of their inside 50s against the Blues, placing Bolton's men fifth behind Adelaide's 42.3 and ahead of the competition average of 47.6.

Those are strong numbers for a club with a 3-4 win-loss record, even if its draw to date of Richmond, Melbourne, Essendon, Gold Coast, Port Adelaide, Sydney and Collingwood helped.

Marchbank, the round-six NAB AFL Rising Star nominee, and Rowe are the resident intercept specialists, but ex-Docker Silvagni has outperformed both in that area since coming into the side a fortnight ago.

That suggests two things: Silvagni is fitting in well and Bolton's talk of the defence being a well-oiled machine is more than just lip service.

"They're a backline that holds a fair bit. They don’t get up the ground and counter-attack heavily," the opposition analyst said.

"They love to outnumber and play a plus-one (a spare player in defence) with a Docherty-type, to provide a real springboard from defence into attack.

"They hold their shape well, and that helps the younger guys."

Jacob Weitering, the No.1 pick in the 2015 NAB AFL Draft, is the most fascinating piece of Carlton's puzzle.

The 195cm rising star showed great promise down back in his rookie season last year, but the club needs him up forward right now.

Do the Blues leave him there to support fellow tall Levi Casboult? Or do they look long term, knowing Rowe turns 30 in November and Marchbank (193cm) is a tad undersized to handle the giant forwards?

That Marchbank has conceded only six goals in seven games in 2017 provides a guide, but the answer might be elsewhere.

Macreadie (196cm) and the forgotten man Kristian Jaksch (195cm) are also among the long-term options to fill Rowe's position down back.

Our opposition analyst has his opinion.

"Young guys in the past have played key defensive posts at Carlton in not a great team and it can drain their confidence," he said.

"Rowe holds on most weeks and is not beaten badly too often, so that keeps Weitering nice and positive.

"Weitering's intercept marking and reading of cues (are very good) ... and he sets up well and is a good communicator.

"There's a fair argument to say he will still end up as a good defender."

Bolton has a decision to make with Weitering.

But if Rowe and co. continue their stingy ways, young forwards Jack Silvagni, Charlie Curnow and Harry McKay can continue their apprenticeships without the pressure of kicking a cricket score.

Carlton's latest rebuild, under the smiling assassin out of the Alastair Clarkson school of coaching, appears to be on track.