WITH A plethora of tall forwards on its list, North Melbourne captain Andrew Swallow says Robbie Tarrant will play as a key defender this season and is a shoo-in for round one. 

Jarrad Waite's off-season signature bolstered a tall forward brigade that already included Drew Petrie, Ben Brown and Aaron Black, putting the squeeze on spots.

But Swallow says Tarrant has been a strong pre-season performer in the back half, and his development is perfect timing to cover the absences of Nathan Grima (back) and Lachie Hansen (hip).

Grima is expected to miss another 10-12 weeks, while Hansen is slated to miss another two, putting him out of the opening match against Adelaide on April 5.

But Swallow says North Melbourne has the depth to fill the void.

"Robbie Tarrant has been training all pre-season down back, so we'll probably pencil him in for a key position spot down back," Swallow told SEN.

"Lachie is starting to move well. I reckon he's a couple of weeks away.

"It'll be nice to get him into some full training and some games, we missed him quite a bit last year.

"But with Robbie Tarrant going back, Joel Tippett as well, and Scott Thompson, we've got enough to cover if Lachie misses a couple early on."

Swallow said the Kangaroos' match committee would have some difficult decisions this season, with Waite and Shaun Higgins bolstering an already deep squad.

The North Melbourne skipper also weighed in on Ryan Crowley's provisional suspension following a positive drugs test.

Swallow said it was a stark reminder how careful players had to be.

"It does get harder and harder every year for players but you've got to be so careful," he said.

"You've got to make sure whatever you put in your body, you tick it off with the doctor.

"At home and you're feeling a bit off and you want a painkiller … you've just got to think twice about it."