All Black and New Zealand sevens star Sonny Bill Williams faces six to nine months on the sidelines following an Achilles injury in New Zealand's shock opening round defeat to Japan at the Rio Olympics today.

Williams limped off with the injury after he took a crash ball into two defenders early in the second half and had to be assisted off the field. After the match it was confirmed his Olympics campaign was over when it was confirmed he a suffered a partial rupture of his Achilles.

New Zealand Rugby chief executive Steve Tew told Mike Hosking on Newstalk ZB that Williams would be sidelined for six to nine months, meaning he won't be playing at all for the All Blacks in the Rugby Championship. He was meant to join the All Blacks after the Olympics ahead of the test second against Australia.

When Williams was helped off it helped "boost" the Japanese players who shocked New Zealand 14-12.


"He's like a main weapon in the New Zealand team so that was our game plan, just try to stop him, especially in offloading." Japan back Lomano Lemeki said.

"Sonny Bill's a good player, no doubt. But we look at every player as a good player on the New Zealand team," he said.

Williams tweeted a message of support for the sevens team along with an image of him holding crutches.

Williams' sister Niall, who won silver with the women's sevens team yesterday, told TVNZ that the All Black second-five will bounce back from the injury.

"I feel for him because we've both been on this journey together. I know the sacrifices, hard work, sweat and tears that have gone into this point of time. I know him, he's pretty tough. He'll get through it and come back bigger and stronger," she told TVNZ.

"He actually told me that the ambulance driver got lost, which was funny and took the edge off. He's not feeling sorry for himself. He's still and Olympian so he can be proud of that."

Joe Webber also looks in doubt to take part in the campaign again after being medi-cabbed off late in the game with a shoulder injury.

New Zealand bounced back from the shock defeat to Japan with a 35-7 win over Kenya. They sit in second behind Great Britain after day one and could top the group with a win in their final group game.

That would mean the shock Japan defeat wouldn't mean little. But this morning things looked much worse.

Just like last year's astonishing Rugby World Cup upset over South Africa, David upset Goliath in an opening pool match which had the Deodoro Stadium crowd in raptures.

"It was unbelievable," said Lemeki after the win over New Zealand. "You never think you would see a minnow team come here and beat a gold medal contender.

"I'm still shocked to be honest."

Captain Scott Curry said they were guilty of making too many mistakes.

"Without the ball it's pretty hard to score and when we got it we knocked it on or turned it over at the ruck."

The All Black Sevens let themselves down with poor handling while the underdog Japanese skillfully controlled the majority of the game by slowing it down to their pace and not allowing the second seeds get into rhythm.

Playing well above themselves, the underdogs scored the opening try but the Kiwi side led 12-7 with two minutes to go before Kameli Soejima crossed out wide and Ktsuyuki Sakai nailed a clutch conversion.

New Zealand almost stole the match at the death with a 90m raid after the siren but heroic defence ultimately ensured another fairytale result.

"That was crazy," Lemeki said. "Everyone was flying just like a kamikaze plane trying to chop their legs off - as long as we didn't let them score a try, if we got knocked out that's fine."

Lemeki felt their dejected opponents took his side lightly, while the result meant the world No.15-ranked side were now serious medal contenders.

"They are going to think they're Superman," he said of his teammates.

It was one of three upsets on captivating day one of the men's sevens with Australia falling 31-14 to France and Argentina also surprising USA 17-14.

"It means any team can win on any day in sevens," Lemeki said. "It's wide open."