For once the All Blacks starting 15 are almost of secondary importance because it is the composition of the reserves bench that has added an element of intrigue ahead of the Bledisloe Cup rugby test at Hong Kong Stadium on Saturday.

Is this year's fourth and final test against Australia an opportune time to introduce Sonny Bill Williams to international rugby?

Unsurprisingly, assistant coach Steve Hansen - who last week urged the travelling media contingent not to prematurely broadcast the team based on what they witnessed at training sessions - would not speculate on whether Williams would feature ahead of tomorrow's team announcement (10.30am AEDT).

"Our thinking at this stage is we'll play Sonny when we feel he's ready to play," a cryptic Hansen said when asked if the strapping league second rower-turned rugby centre would be included on the seven-man bench as midfield cover ahead of Isaia Toeava.

Despite playing only seven provincial games for Canterbury since returning from France with ambitions of playing at next year's World Cup, there is little doubt Williams warrants his inclusion as the only new All Black on tour.

Hansen joined the throng of rugby aficionados and officials to laud Williams' transition to New Zealand rugby from Toulon but reiterated the 25-year-old was still coming to grips with his new environment.

"Like any new person who comes into the All Blacks the intensity is different, the professionalism's different and sometimes that takes a little bit of adjusting to," Hansen said.

Williams, who only met teammates he had not already encountered in domestic rugby during a three-day pre-departure camp in Auckland last week, was assimilating well.

"He's settled in pretty good," said Hansen, and not unexpectedly considering "he's been a professional athlete since he was 15".

The second leg of the Grand Slam attempt against Scotland at Murrayfield on November 14 is anticipated as Williams' starting debutbut the selectors may opt to usher him in the during final quarter of the England test next weekend, or even sooner.

Wallabies assistant coach Jim Williams welcomed the former Kiwi international's involvement on Saturday, although his players were not as enthusiastic.

"It's a matter of timing about when they bring him in, they've got a tough tour with a Grand Slam," Williams said, adding: "It would be great all the same to see him out there."

Wallabies pivot Quade Cooper was wary about the 108kg Williams heading down his defensive channel in the event he replaces Ma'a Nonu.

"He is a giant. He can defend hard, he can put a massive hit on and he can break tackles and offload with one hand. It's crazy. He's got some massive shoulders.

"He's built like a bodybuilder, and prancing and running around, it's not going to be the most exciting thing trying to tackle him.

"Him running off Dan Carter, that's not something I like thinking about."

Meanwhile, both sides are expected to unveil their best available line-ups, barring any dramas at training on Thursday (AEST).

Carter returns to five-eighth after missing last month's Tri-Nations finale in Sydney with an ankle injury; Joe Rokocoko replaces an invalided Israel Dagg on the wing while Jerome Kaino completes the first choice loose trio at the expense of the non-touring Victor Vito.

The Wallabies are expected to make two changes from the side pipped 23-22 in Sydney on September 11, with prop Ben Alexander fit again after suffering a knee injury in June and he will supplant Salesi Ma'afu.

Drew Mitchell is also likely to shunt Lachie Turner from a wing berth after missing the Sydney cliffhanger with a hamstring strain.

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