A trio of former Australian forwards have warned against writing off New Zealand in next month's Anzac Test despite the scratching of Kiwis superstar Sonny Bill Williams.

A day after Williams was officially ruled out with an ankle injury, Queensland great Trevor Gillmeister claimed the Kangaroos could get stung if they took the Kiwis lightly in their trans-Tasman clash at Suncorp Stadium on April 22.

"If the Australian blokes go in there soft they'll be hurt," said Gillmeister, who played three Tests for his country.

"The Kiwis have been pretty good at picking a couple of players out of the blue over the years.

"I always reckon it is a 50-50 bet...in one off Tests."

Glenn Lazarus, one of the finest front rowers of his era, described Williams as an excellent player.

However, he pointed out the teenager had been below his best in recent weeks.

"He hasn't been himself for a while," Lazarus said.

"He would have been at 60 or 70 per cent. A fully fit Sonny Bill Williams is a devastating sort of player.

"But I'm not going to say Sonny Bill is the difference between winning and losing."

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