Sonny Bill Williams © Phil Walter/Getty Images

Sonny Bill Williams has described his transition from dual Rugby World Cup winner with the All Blacks to Olympic Sevens candidate as "tough" but he is "pretty happy with where I'm at the moment".

Williams was named on Monday to make his All Blacks Sevens debut in the Wellington leg of the HSBC World Series on Jan. 30-31. He is expected also to contest the Sydney 7s at Allianz Stadium the following week in his bid to represent New Zealand when Sevens makes its Olympic sport in Rio de Janeiro.

Williams has taken a season off Super Rugby to seek selection for Rio, and his new coach, Sir Gordon Tietjens, says the dual World Cup winner is ahead of schedule in his transition to the seven-a-side game.

Tietjens said the biggest learning area was "just understanding the game", which was so different from 15s rugby, but he was impressed by Williams' "sublime skill sets", work ethic and ability to learn.

Tietjens indicated the 191cm, 108kg former Sydney Roosters and Canterbury NRL premiership back-rower would probably start in the forwards but could equally play in the backs. Williams described Sevens as "just a whole new game". "I'm pretty happy with where I'm at the moment," he said.

FIRST THOUGHTS: What did @sonnybwilliams have to say after being named in the @nz7s squad? Wonder no more.... https://t.co/KDPLgJhCo3

— World Rugby Sevens (@WorldRugby7s) January 25, 2016

"I've still got a lot to learn but the best thing for myself is just to stay healthy and get out there on the training pitch and learn first-hand."

Williams said he wanted to give Sevens his "best shot" and that is why he was concentrating on the game full-time this year. "There are so many talented players, it's going to be really tough to make the Rio squad."

The New Zealand line-up for Wellington also features brothers Akira and Rieko Ioane, who have both played for the All Blacks Sevens but will be making their first appearance together in the same event.

Hurricanes flanker Ardie Savea returns to the side after featuring across six tournaments in 2012.

New Zealand, the most successful Sevens team in World Series history, are seventh on the points table after the first two rounds of this season's 10-tournament circuit, 10 points behind the pace set by Fiji and South Africa but one place and three points ahead of Australia.