New Zealand ace Sonny Bill Williams has been ruled out for up to nine months after rupturing his Achilles tendon during his side's defeat to Japan at Rio 2016.

The 31-year-old, who was the highest-profile name in the rugby sevens tournament at the Olympics, had to be helped from the field during Tuesday's shock 14-12 defeat to Japan in the Kiwis' opener.

Williams was initially ruled out of the remainder of the competition in Brazil, dealing a huge blow to New Zealand's medal hopes, and he has now been told that a return before next April is unlikely.

That means that the two-time World Cup winner will play no part in the All Blacks' Rugby Championship campaign later this year, with a battle on his hands to be fully fit in time for the three-match series against Wales next summer.

Sione Molia was called up to replace Williams, but New Zealand will remain one man down after also losing Joe Webber to a shoulder injury.