NORTH Melbourne's Drew Petrie believes teammate Lachlan Hansen has shown enough in the first three rounds to suggest he'll play the entire season at centre half-back.

Hansen, 20, has been a solid performer in defence after spending 13 games in two years in different positions.

Petrie said that Hansen had matured a lot in recent months and was now pushing to make good on his high selection (No. 3 overall) in the 2006 NAB AFL Draft.

"Lachie's someone who probably just needed a bit of time to develop as a person and then in turn as a footballer," Petrie said.

"He's one of the funniest guys around the club ... but he's toughened up a lot as well.

"He's become more physical as a player, so he's certainly holding centre half-back down really well."

Petrie added that with three pre-seasons under his belt, Hansen should have the conditioning to hold down the key defensive post.

He said that the rigours of the role could provide a challenge later in the year though.

"It might become a bit taxing after a while and [it could] sort of burn out a little bit towards the end of the year," Petrie said.

"But with three years in his legs, he should be right to hang in there for the rest of the year."

Both players were used at centre half-back and centre half-forward throughout the pre-season, but Petrie is pleased that Hansen has made the defensive post his own.

"With Lachie holding down centre half-back, it prevents me from going there but also allows me to play somewhere more regularly," Petrie said. "It's been good.

"I've spent more time in the forward line this year than back.

"We've still got to fix a few things in the forward line but Lachie's enabled a bit more stability in the side."

Petrie said Hansen's improvement had made it difficult for experienced backman Shannon Watt to break into the line-up.

Watt played 21 matches last year to take his career tally to 152, while the use of Michael Firrito and Leigh Harding in the midfield had kept Daniel Harris on the cusp.

"Their attitudes have been outstanding though in just training and still competing and playing VFL footy," Petrie said of Watt and Harris.

"They're only a whisker away."