GEELONG’S much-vaunted defence will be given one of its biggest tests in years this weekend, according to the man entrusted with managing the back half on match day.

Cats defensive coach and former club best and fairest winner Brenton Sanderson says the absence of champion full-back Matthew Scarlett will put extra responsibility on those left to fill the void.

The reigning premiers face Port Adelaide at Skilled Stadium on Sunday minus their two key defenders of 2007.

But while the Cats have known and been able to plan for Matthew Egan’s long-term lay-off, for at least the next fortnight they will have to get by without the services of three-time All-Australian Scarlett.

Scarlett, the general of the Cats’ backline, won’t be present against the Power after tearing a hamstring against North Melbourne last Friday night.

“He’s almost impossible to replace because he’s obviously such a brilliant player,” Sanderson said.

Scarlett has missed seven games since becoming a regular in the Geelong side in 2000 and just three matches since mid-way through the 2001 season.

Sanderson said while Geelong skipper Tom Harley would be marshalling the side, Scarlett’s absence was a chance for the Cats’ back six to show the footy world they were not reliant on the man some have dubbed the greatest full-back of the modern era to lead them each week.

“This produces a new challenge for them and I guess their leader’s going to be out, their defensive leader,” Sanderson said.

“Scarlo obviously runs that backline. Not that they’ll speak about it or anything but I’m sure that they’ll all be aware that they all have to just stand up a little bit more.

“If we can get a small lift from those guys … I’m sure we’ll take it right up to Port.”

This weekend, against a Port Adelaide forward structure featuring the likes of Warren Tredrea, Daniel Motlop, Brett Ebert and Justin Westhoff, the Cats will look to others to lead its defence which has been one of the stingiest of the AFL in recent years.

While experienced duo Darren Milburn and Harley will be there, Sanderson says the workload might have to be more evenly shared.

Sanderson said Harry Taylor and Josh Hunt were likely to come into the side that beat North Melbourne last week, but despite their inclusions the Cats were wary of a dangerous Power side.

“We’ve still got a lot of experience back there. We’ve still got the foundations there for a very strong backline but it’s a real challenge for us without Egan and Scarlett back there.”

Sanderson admitted the Cats had difficulty countering North Melbourne’s tall forwards last week, with David Hale and Drew Petrie causing headaches at different stages.

Port Adelaide does possess height in attack, with Westhoff (198cm) and Tredrea (194cm) having the potential to stretch an under-sized home side.

At 193cm, youngster Harry Taylor is Geelong’s tallest defender but the versatile Tom Lonergan (197cm) – who did spend time in defence last week – might again be called on should the Cats find themselves a little short down back.

“Tommy’s a bit of a swingman for us,” Sanderson said.

“He can go back or forward which is a bit of a luxury for us.

“He’s played most up forward for us when he had come back into the side but he has played some great games in the VFL at centre-half back … Tommy becomes a pretty important player for us as well.”