Fellow rugby convert Timana Tahu says Sonny Bill Williams has put "a target on his forehead", as the former Bulldogs star prepares to use Saturday's Wallabies-Barbarians clash to prove himself in the eyes of his critics.

Tahu, who came up against Williams over four seasons in the NRL, departed from the calm language of the Wallabies hierarchy to declare the league renegade had placed himself in the firing line of a Wallabies onslaught with his media tactics.

"Everyone wants to have a crack at Sonny Bill I think, I think all the press that he's had he's put a target on his forehead," Tahu told reporters.

"He's a big boy, I think it's a big challenge for him more than it is for us to prove to himself that he can play against the best, which he'll be coming up against this week."

Tahu is one option for Wallabies coach Robbie Deans to mark Williams at outside centre, most likely as a replacement later in the match.

Williams, who controversially walked out on the Bulldogs during the 2008 NRL season to join big-spending French club Toulon, agreed with Tahu that he would use Saturday's Sydney Football Stadium match to prove he could play the 15-man game.

"You're always going to have your critics and I think me being a league player playing rugby, they're going to be at me again to see how I go," he told reporters on Monday.

"So I'm definitely going out there to try and have a strong game and just show people I can play rugby."

Asked if that meant he was under extra pressure, the former Kiwis second-rower said: "There's pressure on all of us when we step out on the field. I've just got to learn from this.

"I'm not saying I'm going to go out there and be the star player or anything like that.

"I'm just going to go out there and try and do the basics right and try and learn and not let Stirling Mortlock run through me."

The 23-year-old is expected to be named at No.13 on Wednesday, the position he has played at Toulon after he began his rugby career on the wing.

"At the moment outside centre is where I'm comfortable," he said.

"Maybe in a year or two when I get to know the game a lot more I'll hopefully move in a bit closer to the action."

Barbarians coach David Young, who admitted he had seen little of Williams in action, said "bumps and bruises" to backs Geordan Murphy, Seilala Mapusua and Luke McAlister would be assessed on Tuesday before he finalised his side.

"(Williams has) played a limited amount of rugby union so there's probably still opinions out there where his best position is so we'll have a look at him in training, take into account where we are with injuries amongst the squad and make a decision there - but he'll be in the backs," Young said.

Meanwhile, Williams surprisingly revealed several of his former Bulldogs teammates will be at the SFS to support him.

"A few of the boys will come. I don't want to say their names, they might get in trouble," Williams joked.

"I still support the Bulldogs even though I don't get along with probably the administration but the players, I still back them boys and hopefully they can go all the way this year."

" ... I still have a soft spot for league even though they don't have a soft spot for me."

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