Defender Scott Thompson is the key to North’s defence and 2015 chances, according to The Age and SEN’s Rohan Connolly.

The football journalist believes the Roos still lack strong-bodied key defenders and will need to maintain “stability” in the back six if they’re to challenge this season.

Connolly said Thompson could be the difference in propelling North to a premiership.

“He (Thompson) has been incredibly durable, but if he goes over, I think it really weakens them structurally in the backline,” Connolly told SEN’s Morning Glory on Thursday.

“It means that Lachie Hansen can’t play that loose defending role he did really well last year, and it puts a lot more pressure on Nathan Grima, whose body’s been pretty iffy over the years as well.”

Connolly said the addition of experienced duo Jarrad Waite and Shaun Higgins could significantly strengthen North.

“Higgins is a particularly good recruit because he offers flexibility,” he said.

“They can use him as a rebounding defender, they can use him as a small forward (and he) could even run through the midfield.”

Connolly believes the Roos can win 15 games this season – one more than last year – after finishing sixth on the ladder at the end of the regular season in 2014.

“They beat every other side around them in the top six on the ladder,” he said.

“I don’t see any reason why they can’t go on with it and actually finish the home and away season in the top four.”

The Kangaroos head into the season with the second-oldest list in the League – with an average age of 25.35 years.

“Age is an issue. I think a lot of people don’t realise how old overall they are,” Connolly said.

“They’ll have six players this season who are 30 or older."

Despite several veterans on its list, Connolly said the quality of players in that bracket means North is in a window for potential success.

“The age thing might not be as big a factor as it appears superficially,” he said.

“As far as the on-ball brigade goes, I don’t think the age worries are so much there.

“If the bulk of those 30-plus players were playing in the midfield, that would be a bigger concern than otherwise.”