Sonny Bill Williams
Sonny Bill Williams initially switched to rugby sevens in August 2015David Rogers/Getty Images

New Zealand's hopes of winning the inaugural Olympic rugby sevens men's event have been dealt a further blow after Sonny Bill Williams was officially ruled out of the remainder of Rio 2016 due to an achilles injury.

The powerful 31-year-old, a two-time World Cup winner in the 15-man version of the sport who has switched codes on numerous occasions and also boasts an unbeaten record in seven fights as a heavyweight boxer, was helped off the field after hurting himself while taking the ball into contact against two defenders during the second half of a shock 14-12 opening defeat to Japan.

Such a stunning result rather invoked memories of the Brave Blossoms' historic defeat of South Africa in Brighton last year that went down as easily the biggest shock in rugby history.

Fears that he would play no further part in the competition were subsequently confirmed in a tweet from the New Zealand Olympic team, which read: "NZ sevens injury update. Sonny Bill Williams ruled out with partial achilles rupture."

Williams has now been replaced by travelling reserve Sione Molia. The All Blacks, who will look to avenge that massive upset against Kenya later on Tuesday evening (9 August) at the Deodoro Stadium, also lost centre Joe Webber to a shoulder injury.

Great Britain are next to meet Japan after thrashing the Kenyans 31-7 in their Pool C debut earlier this afternoon. Dan Norton, Dan Bibby, Mark Bennett and Phil Burgess all registered tries for Simon Amor's side. The Team GB women failed to claim a medal on Monday night after a semi-final defeat by New Zealand was followed by a desperately disappointing 33-10 loss to Canada in the bronze medal match.