Sonny Bill Williams' status was as unpredictable as ever when the Wallabies started preparations for Saturday's Bledisloe Cup and Rugby Championship test in Sydney although doubts about his availability were offset by the guaranteed absence of the All Blacks' understated midfield maestro.

The Wallabies backs were as puzzled as their opponents regarding the prospect of Williams prolonging his All Blacks career at ANZ Stadium before he returns to the NRL via Japanese club rugby.

His offensive capabilities are highly regarded in Australia but even if Williams was granted permission by the Panasonic Wild Knights to assist the All Blacks defend the trans-Tasman silverware in Sydney and Auckland, the Wallabies feel they could have an edge out wide because Conrad Smith will be missing as he recovers from eye surgery.

The 30-year-old centre boasts the highest winning percentage of a current test player with more than 50 caps (89.65 per cent) yet Smith, who is 11-3 against the Wallabies, is much more than a lucky charm for the All Blacks.

Experienced Wallabies utility back Adam Ashley-Cooper has marked Smith only five times in 17 tests against the All Blacks and is glad to see the back of the linchpin until the third Bledisloe test at Brisbane in October.

'It's a great bonus,' Ashley- Cooper, who is likely to be selected on the wing, said.

'He's one of the best outside centres in the game, his work rate is unbelievable.

'He actually keeps that backline together, he's the most crucial link between the midfield and the outside backs.'

Smith, a 58-test veteran, will never attract the same superlatives as Williams but Ashley-Cooper marvels at the All Blacks' quiet achiever.

'He's a competitor. In every moment he competes and that's why he gets the job week-in week-out. Conrad does a lot of off-the-ball stuff people don't realise.

'He's never recognised by the public or the commentary but when you know the game and you understand someone's role . . . Conrad is a bloke who gets through a shitload of work.

'He might not be brilliant like Sonny Bill in one particular aspect of his game but he's got every part of his game covered.' Ashley-Cooper figured Williams or Ma'a Nonu would start at centre, depending on the former's availability.

'It will be testing times for that backline without Conrad, regardless. They'll miss him, luckily for us.'

The Wallabies, meanwhile, have their own backline issues with utility James O'Connor ruled out, no frills second five-eighth Pat McCabe succumbing to a stress fracture and Quade Cooper underdone since his comeback from a serious knee injury.

Ashley-Cooper said the Wallabies were eager to take the first step towards securing the Bledisloe Cup for the first time since 2003. 'Sharpie's [lock Nathan Sharpe] the only bloke who's held it, it's something we've never experienced before and something we want badly,' he said.

- © Fairfax NZ News