RIO DE JANEIRO (AP) — Sonny Bill Williams dedicated a season to prepare for Rio. When the Olympic rugby sevens competition finally kicked off, he spent about eight minutes on the field.

Now he'll be sidelined for up to nine months with an injured Achilles tendon, ruling him out for the All Blacks in 2016.

The highest-profile player in rugby's return to the Olympics after 92 years carried the ball into a tackle early in the second half of New Zealand's 14-12 upset loss to Japan on Tuesday, then stayed on the ground holding his left ankle before being helped from the field.

A despondent Williams was taken to a hospital and medical tests showed a partially ruptured Achilles tendon, which is expected to keep him on the sidelines for up to nine months.

"He's obviously shattered and disappointed," New Zealand coach Gordon Tietjens said.

Not long after Williams' exit, his teammates left the Deodoro Stadium with their heads down, having lost to Japan for the first time in rugby sevens.

A two-time Rugby World Cup winner with the All Blacks in 15s, Williams had little impact on the Olympics. His sister, Niall Williams, picked up a silver medal as part of the New Zealand team which lost the women's gold-medal match to Australia the previous night.

"Devastating for Sonny, to lose him so early in the tournament," New Zealand coach Gordon Tietjens said, added that the shoulder injury to Joe Webber was also a major setback. "Both influential players as well, got some outstanding qualities that I needed."

The New Zealanders rallied to beat Kenya 28-5, but now face unbeaten Britain on Wednesday in the last Pool C game.

"We've just got to get on with it," Tietjens said. "The guys bounced back with a lot of character against Kenya."

But they'll have to do with one man down in the squad, with only one replacement allowed. Sione Molia was called in to replace Williams.

Tietjens said Japan showed against his team and in the narrow 21-19 loss to Britain that the competition was intense for the medals.

"They're a good team. They pushed Britain very closely as well — perhaps that says it all," he said. "There are no given games these days.

"I knew with Kenya and Britain, there was a chance we weren't even going to look at the quarterfinals, so we've got a chance tomorrow to get in there."

The New Zealanders were hoping to have Williams back around the team in some way during the Olympics.

"He's a great professional. Very infectious. He's certainly helps the younger players. He's got a great work ethic," Tietjens said. "For that (injury) to happen in the first game of the tournament is devastating.

"We've struck an horrendous amount of injuries this year in the world series as well but there's a lot of character in this team, I can assure you."

New Zealand Rugby Union chief executive told Newstalk ZB Radio that Williams would be out of action for six to nine months and selectors would have to find a replacement for the All Blacks squad to play in the Rugby Championship.