Wellington: The All Blacks have called up uncapped Waikato Chiefs midfield back Anton Lienert-Brown to their squad for the Rugby Championship to replace the injured Sonny Bill Williams.

Two-times World Cup winner Williams partially tore his Achilles tendon during the rugby sevens tournament at the Rio de Janeiro Olympics and was ruled out of action for anywhere between six and nine months.

The All Blacks sevens side were knocked out in the quarter-finals in Rio.

The 21-year-old Lienert-Brown had been brought into the All Blacks camp last week to train with the squad, and his ability to play both midfield positions had earned him the nod ahead of Chiefs team mate Seta Tamanivalu, who is a specialist centre.

Tamanivalu played two tests in the June series against Wales.

"The reason why we have gone for Anton is because he can play second five and centre and he gives us better options there," coach Steve Hansen told reporters in Auckland on Thursday.

The All Blacks begin the Rugby Championship on Aug. 20 against Australia in Sydney, and Hansen had been counting on Williams joining the team ahead of their second clash, also against the Wallabies, in Wellington on Aug. 27.

The 31-year-old had committed to the sevens programme full time and not played any 15-aside rugby this season.

Hansen, however, said there could be a silver lining in Williams' enforced absence, given that he has played rugby union, rugby league and sevens virtually non-stop for the past six years.

"If you look at the positive side for Sonny it gives him now six or seven months where his body gets a break," Hansen said.

"He probably hasn't had that for a long time because he's such a good athlete right across the field, he does so many different things so eight or nine months off probably won't hurt him.

"It might frustrate him, but it won't hurt him."