North Melbourne big man Drew Petrie has declared he wants to play on next year, but the key forward knows he'll have to prove himself in the remaining part of this season.

Petrie, who turns 34 in October, has been down on form, and with spearhead Jarrad Waite also keen to extend his career into 2017, appears the most vulnerable of the Kangaroos' tall forwards.

But the 307-game veteran hasn't given up on earning another contract and insists he's got the desire to play for a 17th season.

"I do. I've got to show that with what happens in the next eight-plus weeks for the year," Petrie told RSN radio.

Petrie has appeared in all 14 games this year but has only kicked 19 goals – on track for his lowest full-season total since 2009 – and is averaging just 4.6 marks.

"The numbers like that and my marks are a lot down on what I expect," he said.

"Last I year took the most marks I have in any season (168 at seven per game), so I was hoping to be able to beat that again.

"But at the moment those numbers aren't looking too well.

"I'm aware of how I'm going and I'm looking forward to the next eight weeks and setting some goals in place to make sure that I can contribute a little bit more than what I have in the first half of the season."

Petrie is still rarely out-marked, and laid five tackles, a season-high, in the loss to Adelaide before the bye, showing his determination to get his season going and to help the Roos turn around their slip from the top of the ladder to seventh.

"If you rely on kicking a goal or taking a big mark to get yourself into the game, often you can be waiting a while, especially if the footy's not coming down your end," he said.

"So you've got to find other ways to bring yourself into the game.

"There's a big emphasis on tackling for all our players … and the Adelaide game was on the back of the Hawthorn game when we tried to have our highest tackle count for the year.

"So we had to prove to ourselves we could carry that attitude (against Hawthorn) over to the next game."

Petrie revealed that he had turned to evergreen teammate Brent Harvey for advice during his trying campaign, but also much-maligned small forward Lindsay Thomas.

"You lean on those blokes that you've played with for longer periods of time – in my case it's Boomer (Harvey)," Petrie said.

"We know each other really well.

"Other forwards as well. Lindsay Thomas is great at encouraging all the forwards, but me in particular when things aren't going so well."

Petrie has booted 420 goals over his career and the Kangaroos need the popular 197cm big man to rediscover his best for the critical trip west to face West Coast on Sunday, with Waite under a fitness cloud.

Waite (hip) has missed the past two matches, while classy onballer Daniel Wells (calf) is also pushing to be fit for the Eagles clash.