All Blacks scotch Sonny Bill injury rumours

New Zealand's assistant coach on Sunday quashed rumours that star centre Sonny Bill Williams had suffered a World Cup-threatening injury, declaring him fit for selection for the All Blacks' crunch opener against South Africa.

Social media in New Zealand has been abuzz with reports that Williams was heading home, which would have been the second injury blow for the defending champions after losing flanker Luke Jacobson.

But Ian Foster denied the reports.

"Is he going home? No. Is he available for selection based on his progression last week, then I think the answer is yes. He's trained really well," he said.

Foster stressed that no one had been called up from New Zealand because "there are no people needed".

He insisted that nothing but victory was acceptable in New Zealand's marquee Pool B match against the Springboks.

"It doesn't mean you've finished if you don't get the result, of course it doesn't. It's a tournament. But that's not the way we're thinking," Foster told reporters.

"We're thinking this is an outstanding opportunity to go out there and test ourselves straightaway in this championship."

Meanwhile, playmaker Beauden Barrett revealed the All Blacks had been focusing on playing with a wet ball in training, as torrential rain is forecast at the weekend when the key games get under way.

He said he expects to get pelted with high balls if he plays at fullback and has been preparing intensively.

The All Blacks star said he was equally happy to occupy the fullback or fly half position and was relishing the higher profile he now enjoys in world rugby.

Barrett's role was mainly confined to an impact sub utility back at the last World Cup and he hopes to take on more responsibility this time.

"Four years later, I'm older, more experienced, with a little bit more responsibility on my shoulders," said the 28-year-old. "It's a challenge I really enjoy."