THEY are the Patchwork Pies, a band of defenders with far more responsibility than they were ever supposed to have.

(Now read that again in your most theatrical, deep voice, as if you were narrating the trailer for a blockbuster movie.)

This same, unheralded group – think Tom Langdon and Brayden Maynard – also holds the key to delivering Collingwood's first Grand Final berth in seven years, and maybe a first premiership since 2010.

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Season-ending knee injuries to Lynden Dunn and Matt Scharenberg forced most of them to step up, but that's not the sum of this story.

Jeremy Howe, Darcy Moore, Tyson Goldsack, James Aish and Sam Murray also missed extended periods at various stages.

Making matters worse, 2011 All Australian centre half-back Ben Reid, who was playing forward but would have been a backline option, last played in round 10 because of knee and calf problems.

Matt Scharenberg was only one of many winged Magpie defenders this season. Picture: AFL Photos

The Magpies' back seven in Saturday night's semi-final triumph over Greater Western Sydney was Maynard, Langdon, Goldsack – in his second game back, six months after a knee reconstruction – Jack Crisp, Howe and Aish.

We've also seen the likes of ex-basketballer Jack Madgen, Flynn Appleby, Adam Oxley and Nathan Murphy down back through this torrid period, with only Murphy not on the rookie list.

So how have they fared, using Dunn's absence since his round 15 injury as the point of contrast?

Those numbers suggest they're holding up remarkably well and are, perhaps, a harder-working unit than before, although the marks conceded in their defensive 50 are cause for concern.

It is exacerbated when you factor in that half of their 46 defensive one-on-one losses were marks in that timeframe, so there is an aerial issue.

The tumble in intercept marks almost entirely owes to Howe's month-long stint out recovering from a seriously corked thigh that required surgery.

Langdon, undersized at 189cm for the role he's performing, is the glue holding the club's defensive foundations together in the past 10 matches.

His assortment of opponents in that time include Brett Deledio, Jack Darling, Matt Taberner, Robbie Gray, Eric Hipwood, Lance Franklin, Josh Caddy and Jack Ziebell.

Langdon ranks No.1 in the AFL for defensive-50 groundball-gets, third for intercept possessions and seventh for spoils since round 16, while Maynard neutralised Giants star Toby Greene at the weekend.

Goldsack's made a difference in the past fortnight, too, losing just one of his five one-on-one contests and being a major contributor in several areas.

But now comes the biggest challenge – beating reigning premier Richmond in a preliminary final, including solving the Jack Riewoldt riddle.

Part of that solution might mean rolling the dice on Moore's hamstrings, knowing he hasn't played since round 20 and in only seven games in 2018.

Moore and Howe shared the job on Riewoldt in round 19, becoming the sixth and seventh Collingwood defenders tried on the triple Coleman medallist in their past five clashes.

Riewoldt has kicked 26 goals in nine games against the Pies since 2013 (and never fewer than two) – the most of any player – and his total scoreboard impact of 238 points against them is also No.1 in the League.

The ground-level battle will also be fascinating, given the Tigers rank second for forward-50 crumbing possessions, while Collingwood is the League pacesetter for defensive-50 crumbs.

Richmond kicks 47 per cent of its goals from general play, as opposed to set shots, whereas the Pies allow their opposition to score only 39 per cent of goals that way.

Improved Demon terrorising opponents

Melbourne's flavour-of-the-month midfielder James Harmes has the AFL's finals tackles record in his sights.

Harmes laid 11 tackles against Hawthorn and 10 against Geelong to make him one of four players with double-digit tackles in consecutive finals since Champion Data began recording them in 1999.

The others were Lenny Hayes (2010), Ryan O'Keefe (2012) and Liam Shiels (2016), while former Footscray hard man Tony Liberatore also managed the feat in 1992.

No player has done so in three straight post-season matches, and Harmes is also halfway to Hayes' 2010 finals record of 42 from four games.

It's all about the contest for Giants

Greater Western Sydney lived or died in the contest this year, which is why coach Leon Cameron placed such focus on it after the club's last two losses to Melbourne and Collingwood.

Cameron's men sit with those two clubs as the AFL's premier contested possession sides, but suffered lopsided defeats to them in that area against the Dees in round 23 (111-139) and in Saturday night's semi-final against the Pies (136-158).

The Giants boast 11 wins and one draw from 24 matches in 2018 when they win more contested ball than their opponents, but that slips to a 3-5 record when they lose the count.

They won just one of six games when they conceded contested possession by five or more this season.

Hawks will be kicking themselves

Hawthorn recorded two of its five worst performances in forward-half kicking efficiency in bowing out of September in straight sets for the second time in three years.

Alastair Clarkson's men went at just 52.6 per cent efficiency against Melbourne on Friday night after going at a season-worst 46.8 per cent in the previous week's loss to Richmond.

Their forward-half kicking efficiency across the two finals was just 50 per cent, way down from their 59.7 per cent mark in the home and away season.