No easy World Cup games - Williams

Sonny Bill Williams made an instant impact as New Zealand opened their World Cup defence with victory against Argentina, but says there is plenty of work to do.

Williams, who has flitted between codes and had a spell in the NRL with Sydney Roosters after helping the All Blacks win the 2011 World Cup on home soil, provided plenty of attacking impetus when he came on at Wembley in the 26-16 win.

But the 30-year-old says New Zealand are aware, after South Africa's shock loss to Japan on Saturday, that the rest of their Pool C contests are not a formality as Namibia, Georgia and Tonga will prove stern tests.

"We're just a work in progress," Williams said.

"As we saw with Japan and South Africa, the gap between the lower tier teams and the higher ranked teams is not as big any more.

"Any team on their day can upset any other team. We've a lot of things to work on, but overall we're excited just to be here."

Williams was introduced early in the second half and made his mark as the All Blacks camped in the Pumas' territory.

He is now only looking forward, with Namibia next up at London's Olympic Stadium on Thursday.

"I was just excited to be a part of it," he said.

"I'm really excited and pumped to be here. I got on a bit earlier than expected and just tried to do my job as best as I could.

"It was a tough day at the office. We'll take that win and move on."

Williams provided the final pass for a try by replacement Sam Cane and earlier should have laid on another with a trademark offload, but, in the words of All Blacks head coach Steve Hansen, Nehe Milner-Skudder "butchered" the chance.

Wing Milner-Skudder said: "I thought he was going to carry it. I bombed that one."

Milner-Skudder was sharing a room with Williams last week and has been on the receiving end of some teasing of a different nature.

"During the week he got a bit of a bad haircut and I keep geeing him up," Williams said.

"He was in a bad mood all week, until Nuggie (scrum-half Aaron Smith) fixed it. I was geeing him up more about that than anything else.

"A few times we could've got over the line. It was just that last pass or effort. I thought Nehe played outstanding."

Argentina play Georgia, who opened with a defeat of Tonga and will be a challenging test.

Head coach Daniel Hourcade plans to field his best available side in Gloucester, with lock Guido Petti likely to undergo concussion protocols after taking a blow to the head in scoring his side's first-half try.

"With regards to the game with Georgia, we'll have the best team," Hourcade said.

"Now we need to check those players who have been injured.

"After watching Georgia we know they're strong. We'll stay calm, assess the team. We'll use the best team available. And this is nothing new."