AS SYDNEY grapples with an injury crisis in its talls department, its smallest player looms as a key figure in its plan to stop one of the biggest and best forward duos in the competition.

For the second week in a row, the Swans will be forced to take an undersized backline into Saturday night's showdown against Geelong. But if last week's win against Richmond is anything to go by, Sydney's makeshift system can stand strong despite a lack of key personnel.

Saturday, however, is a slightly different prospect as the Swans prepare to face the Cats, who dismantled them in the Grand Final just seven months ago.

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Although Richmond's attack was somewhat depleted last Friday night and relied on youth around veteran Jack Riewoldt, the system Sydney's defence relied upon was sound, and one it will need to lean on again if it is to quell the Cats' potent forward line.

Without key pillars Tom and Paddy McCartin and main organiser Dane Rampe, Sydney's defensive unit had to restructure last Friday. Nick Blakey was forced to play as a key back, Robbie Fox was needed as the reliable anchor, Callum Mills went back to his defensive roots and wingers Justin McInerney, Matt Roberts and Dylan Stephens all worked hard to support.

Typically, when the safety blanket of the McCartin brothers and Rampe is there, the rest of the defensive line is given a license to attack and looks to play on and generate run from the back half. Blakey, Jake Lloyd and even Oliver Florent have made aggressive rebounding runs through the corridor hallmarks of their game in recent years.

A necessary mindset shift last Friday for Blakey in particular, however, was about defending first and foremost.

Between rounds one and four this year, Blakey played on from 41.2 per cent of his marks, up nearly 10 per cent on last year's number. Against Richmond, however, his changing role was reflected in that metric falling to zero.

Giving up height against Samson Ryan and strength when matched with Riewoldt, Blakey registered seven spoils to go with Fox's eight, with the pair bringing the ball to ground to allow Sydney's smaller contingent to get to work.

Blakey and Fox found an instant chemistry and provided strength and composure behind the ball. But without Blakey's rebounding mindset, others had to step up.

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Third-year player Braeden Campbell has found his place in the Swans' defence and took on that aggressive rebounding role, gaining 511 metres from his 20 disposals. Meanwhile, Mills had the task of minimising Dustin Martin's impact in attack, while also working up the field at times.

This team synergy, avoiding isolating defenders in one-on-ones and forcing the ball to ground will all be vital against the powerful Geelong attack this weekend. Looming large is key forward duo Jeremy Cameron and Tom Hawkins, who could be the responsibility of Blakey and Fox respectively. Fox did a solid job on Cameron in the Grand Final and was one of the few Swans to perform their role as the Cats surged to the flag. However, the shortage of other talls may force the 185cm defender onto the big-bodied Hawkins in the forward 50 instead of up the ground against the versatile Cameron.

Whatever the one-on-one match-ups are, limiting the impact of the dangerous Cats duo will be a team-wide task. It starts with increased forward pressure and compressing the ground in the Swans' front half to starve Geelong's forwards of opportunity. That territory game was something Sydney won last week by winning the footy at the source, applying pressure to Richmond's defenders looking to rebound, and setting up across the width of the ground to intercept attempts to exit.

Against Richmond, Sydney averaged a tackle inside 50 from 21.9 per cent of its forward entries, it's second-highest average of the season to date and a whopping 11.5 per cent improvement on the week prior.

The forward and midfield group were responsible for that pressure inside 50; Isaac Heeney led the way with four tackles inside 50, while four other players registered two for the game.

And while the intercepting layer sitting outside the 50m arc was largely instigated by the back six, Errol Gulden also played a vital role. As a forward-turned-midfielder, Gulden regularly pushes hard forward after the stoppage has been won. Instead, against Richmond, he tended to sit back outside the forward 50 and assist in that intercept game and was then often responsible for delivering the ball back into attack.

Maintaining the territory game comes back to controlling stoppages and preventing any fast breaks from the Cats who, although sitting 12th in the competition for points from stoppages, are fifth for scores from centre stoppages.

Should the ball break through those first two defensive layers, the Swans must work to support Fox and Blakey by slowing the Cats' forward movement, blocking leading lanes and maintaining an active presence at the fall of the ball.

If Sydney is to allow quick, attacking play from centre stoppages, it will expose its vulnerability in one-on-one contests and give Cameron and Hawkins the upper hand.

But if the Swans can once again find the full team defence that spurred its win against Richmond, they are every chance of getting one back on the Cats in in the teams' first meeting since Grand Final day.