Michael Firrito says the Roos will need to pay great respect to last year's minor premier, Fremantle, despite its injury concerns.

Ross Lyon’s side will head to Etihad Stadium on Sunday to take on North, without captain David Mundy and ruckman Aaron Sandilands, but despite their winless start to the season, Firrito is expecting a tight battle.

“We know how proud they are, and how much fight they have,” the Roos' defender said on Monday.

“We know what sort of footy club they are and how well led they are.

“They are under the pump a little bit and have their backs to the wall, so we’ll need to be at our very best again.

“We expect a ferocious Fremantle side to make the trip over.”

North goes into the match undefeated, after their perfect run continued with a five-point win over Melbourne yesterday.

Despite the team's fast start, Firrito said there was still plenty of room for improvement.

“To be honest, it doesn’t feel like we are playing great footy. It doesn’t feel like it’s that far away, so we’ve got plenty to work on,” he said.

“But it’s good to be on the positive side and off to an unblemished start.”

Yesterday’s win in Tasmania saw North extend its winning streak over Melbourne to 15.

“We knew Melbourne would throw everything at us. They were ferocious at the footy, and they won contested ball and inside 50s and we were probably a little lucky to get the win,” Firrito said.

“I think the way we defended, there was a heap of inside 50's and to nullify a few of them was pretty good.

“There was some pivotal plays (in the closing seconds). Cunnington got into the back 50 and Lindsay Thomas at the end with that spoil, it was a game saving spoil. (There are) certainly positives to take out of it, but we don’t probably want the opposition scoring as heavily as they did.”

The number 11 suggested the recent run of shootouts, including yesterday’s 41-goal thriller, was partly a result of rule changes implemented this season.

“I guess that’s what the AFL want and they want to see high-scoring games,” Firrito added.

“I’m sure the fans are pretty excited with it, (but) being a defender I probably don’t want to see the big shootouts.

“The game is significantly quicker, I feel. It’s appealing for fans, crowd numbers are going up, memberships are going up so I guess it’s really good for the game.”