Dermott Brereton says North Melbourne has a secret weapon of sorts in its arsenal to defeat Sydney on Saturday night.

The former champion Hawks believes Kangaroo vice-captain Jack Ziebell is the player with the ability to change the game at ANZ Stadium.

"You need to win the ball, so you need a blend of power, physical prowess, courage and firepower to take it up to the Swans," he wrote in his Herald Sun column.

"And the player with these attributes that has slid under the radar is Jack Ziebell."

Brereton says Ziebell has been quiet against the Swans over his career and needs to stand up in the semi final.

"Ziebell has kicked goals against every team in the AFL except one — Sydney," Brereton wrote.

"Since his debut season he has averaged only 17 possessions a game against the Swans — pretty low numbers for a full-time midfielder. Last week, against the Tigers, Ziebell picked up 23 touches."

Possessions aside, Brereton said Ziebell can do some real damage with his attack on the ball and player.

"Ziebell is tough, hard at the ball and has a touch of “killer’ in him for those opponents camped in the wrong spot or accidentally set up by their teammates."

Last year's humiliation in the prelim at the same venue will spur Ziebell and the Roos on in Brereton's opinion.

"Ziebell is now 24 and has played more than 120 games. He should be motivated by what happened at this very venue exactly one year ago against the Swans.

"He and his teammates were ridiculed by an overtly physical Sydney. Ziebell’s time is now.

"Ziebell needs to gather double-figure contested possessions and, at the same time, throw his weight around by crunching packs or legally pounding players.

"And, for the first time ever against the Swans, he needs to snag a goal or two."