The new league added an extra layer of governance, creating a clunky structure that is beginning to pose problems.
Castle was quick to stress the game is not "broken", but she believes Netball NZ needs to be proactive and begin discussions about change now to ensure the sport does not reach crisis point.
"The environment is changing around us, the ANZ Championship has overlaid an extra layer into our structure and we don't think the current model we've got can take us through another 10 years," said Castle.
"I think we can see problems occurring if we left it as it is, but the good thing is that we're not broken now, so we're in a really good place to make these decisions."
At present the country is divided into 12 netball regions, each with its own administration and board. The arrival of the transtasman league saw five separate franchises established to sit alongside the regional structure, creating a messy arrangement.
The Northern Mystics, for instance, are made up of three regions - Netball North, Auckland Waitakere and Counties Manukau. But the Mystics and each of the three regions are run by separate administrations and governed by separate boards.
Multiply that structure around the country and you end up with 17 separate governing bodies - five franchises and 12 regional - and very real concerns that resources are being wasted.
Another key driver of the change is the need to hand the sense of responsibility for the franchises back to the regions. Over the competition's first four years Netball NZ has been called on far too often to prop up ANZ teams.
The six-figure bail-out of the Pulse is the most high-profile example, but other teams are also heavily reliant on the support of the national body. Netball NZ had to underwrite a $200,000 overdraft for the Magic, while the Canterbury Tactix are also facing financial hardship in the wake of the Christchurch earthquake.
The push to shift the power back to the regions is based on growing recognition that Netball NZ needs to cut the umbilical cord to the franchises and get back to running the game.
While moving to a zone-based model makes sense both practically and financially, Castle will face a political battle trying to get the proposal approved at council level.
Members will vote on the proposal at an annual meeting in February and will need support of two-thirds of the delegates for it to be passed. But that will require some members to effectively vote themselves out of a job.
So Netball NZ's big challenge over the next few months will be convincing members to vote in the interests of the game, rather than self-preservation.
