With just two tournaments to go, the Aussies (66 points) trail the Kiwis by 10 points.
Aussie coach Tim Walsh said Staples' abilities immediately drew attention and he is hoping she can provide an edge.
"Cassie is a unique talent, and a perfect example of the kind of athlete we want to unearth," Walsh said.
"She's fast, tough and agile but also, more importantly, has a real point of difference."
Walsh hopes her addition to the side for Canada will help the team lift for their first series win this tournament.
"We haven't performed to our standards this season and we have to own that and live with that. We're fully focused on this tournament," he said.
Current points standings:
New Zealand 76 points
Australia 66
Canada 64
Fiji 50
Russia 46
USA 42
France 32
England 30
Ireland 20
Spain 12