Where to now for the Silver Ferns?

The former New Zealand netball coach Yvonne Willering says current Silver Ferns coach Janine Southby is seemingly bereft of solutions as she tries to turn the side's fortunes around.

The Silver Ferns are on the verge of a series whitewash at the hands of Australia in the Constellation Cup with the fourth and final test in Sydney tomorrow night.

A 12 goal loss to the Diamonds in Adelaide on Wednesday night forced Southby to make a myriad of substitutions as she tried to find a winning line-up.

Willering says Southby is obviously frustrated by the players inability to implement the game plans she wants.

"At the moment they're trying to play safe netball, but be doing that they've got no ball speed and you can see that that's what's happening."

"No one wants to make a mistake, but by doing that you're losing your team cohesion on that," Willering said.

"In that last quarter New Zealand made far too many substitutions and I just didn't understand the reasoning behind them because (Katrina) Grant going to wing defence - I can't see her playing there during the Commonwealth Games....if it was just a question of getting players on court I don't buy into that because we still had opportunities (to win) and we don't want that big a score differential."

Willering said Soutby still plainly doesn't know what her best starting seven is but hopes she doesn't use the fourth test to continue experimenting.

"They've got to have urgency but I just hope they stay focused on performance rather than the score...the Constellation Cup is gone but they need to get some credibility back, some pride in themselves and I guess some belief."

Willering wasn't impressed with the third Test.

"I didn't think it was a great game, especially in the first quarter when both sides made a lot of mistakes, however Australia managed to settle down better than New Zealand."