The All Blacks have suffered a major injury blow, with Sonny Bill Williams ruled out for up to nine months with an Achilles injury.

Williams suffered the injury during New Zealand's opening Olympic rugby sevens match against Japan in Rio.

NZ Rugby Union CEO Steve Tew confirmed the news on Wednesday morning.

“He has a partial rupture of his Achilles tendon, which means he will be out of rugby for six to nine months,” Tew said on New Zealand's Newstalk ZB Radio.

The injury rules Williams out of the All Blacks' Rugby Championship and Bledisloe Cup series against Australia.