After a shock defeat by Japan and the loss of Sonny Bill Williams to injury the All Black Sevens have got their Rio campaign back on track with a 28-5 hammering of Kenya.

The four tries to one win was desperately needed after Japan had stunned them 14-12 in their opener and Williams exited the tournament with a partially ruptured Achilles tendon. New Zealand were also put under immense pressure in their second pool match and made a host of uncharacteristic mistakes against Kenya before kicking clear.

The Kenyans were up 5-0 until they lost a man to the sin-bin for a high tackle as Scott Curry when to score in the corner and were awarded a penalty try.

Akira Ioane crossed soon after for a 14-5 lead but the Kenyans, who were thrashed 31-7 by Great Britain in their earlier match, continued to frustrate the world No.2 side.


Japan almost pulled off their second upset of the day but a missed conversion after fulltime cost them a draw with GB, who won 21-19.

But they will savour the defeat of New Zealand, just as they did when they toppled the Springboks at the Rugby World Cup.

"It was unbelievable," said Japan back Lomano Lemeki. "You never think you would see a minnow team come here and beat a gold medal contender.

"I'm still shocked to be honest."

Williams was ruled out for the rest of the tournament with the serious injury after he took a crash ball into two defenders early in the second half.

The woes did not end there with Joe Webber dislocating a shoulder in the defeat. 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."

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.

NZ 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."

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."