'A lot more accountability on defence': Quade Cooper faces tough transition to Sevens - Tietjens

All Blacks Sevens coach Sir Gordon Tietjens says there's only one way to transform a good 15-a-side rugby player into a great Sevens athlete.

It's the road Sonny Bill Williams is taking as he chases his Rio Olympics dream, and it's the road former Wallabies playmaker Quade Cooper will have to travel as well.

Despite flying in from French club Toulon on Wednesday, New Zealand-born Cooper has been left out of Australia's squad for this weekend's Sydney leg of the Sevens World Series.

"You've got to play lots and lots of sevens, and train lots of sevens to be good at sevens," Tietjens said.

"Quade Cooper's got all the skill sets to be a fine sevens player. It's the conditioning factors he'll have to get used to - eating, breathing, sleeping and training sevens.

"There's a lot more accountability around defence, so you're challenged a lot more. You can't cover yourself up out on the sevens field, so he'll be challenged there."

In his first sevens outing last weekend, Williams mixed the odd moment of offloading magic with a few too many errors as New Zealand stole a last-gasp 24-21 win over South Africa in the Wellington final.

But Tietjens has kept faith with the 30-year-old sevens rookie, saying he had showed more than enough in Wellington to demonstrate his potential.

"Sonny Bill Williams, from my perspective, is certainly a big pass mark for someone who's never played the game of sevens," Tietjens said on Thursday in Sydney.

"He's a real professional and he gave me everything that I wanted. It's a pretty good start to his sevens career."

Tietjens said Williams brought impressive physicality to sevens, and a very solid defensive game. His versatility was also a huge bonus, with the former NRL star equally at home in the forwards or the backs.

"He's a big tackler and he's very, very good in contact, so anything else he can add on top of that is a real bonus."

New Zealand's win in Wellington took them to third in the world series standings, seven points behind leaders South Africa and five adrift of Fiji.

They will face Australia, Canada and Portugal in pool A in Sydney on Saturday in the fourth of the nine Sevens World Series tournaments.