All Blacks coach Steve Hansen has leapt to Sonny Bill Williams' defence after critics suggested the cross-code star was in decline and should be dropped.

New Zealand media accused Williams of lacking his trademark attacking flair after the All Blacks' nail-biting 25-24 win over South Africa earlier this month.

New Zealand Herald columnist Chris Rattue said that 32-year-old Williams was "already on old legs", while the Dominion Post's Mark Reason said he was "a turnover waiting to happen".

Hansen was having none of it when he arrived in Brisbane on Monday night ahead of Saturday's Bledisloe Cup clash with Australia.

He said Williams could not win -- if he attacked, he was being "flashy" and if he knuckled down in defence, he was accused of going into his shell.

"When he is a flashy player everyone moans about him being too flashy, and that he doesn't do the hard work," Hansen told reporters.

"At the moment he is doing all the hard work and probably not as much as the other stuff that people get excited about."

He admitted Williams -- a two-time World Cup winner who has twice switched between rugby league and union while pursuing a boxing career -- had always been a polarising figure.

"It is a 50-50 split," the coach said. "When he does things wrong all the haters get on top of it, and when he does things right all the good guys get on top of it."

Hansen also praised Williams professionalism in coming back from an Achilles injury, saying he set a valuable off-field example to for teammates.

"He's in the leadership group, he's leading well. He has a major influence on the young guys and training habits etc," he said.

"We are quite happy with him."

Hansen also revealed Beauden Barrett remained in doubt for the Wallabies match because he was still suffering headaches after sustaining a head knock against South Africa.

"We'll see how he goes during the week and if he's not right he won't play," Hansen said.

"He'll have to pass the tests we do as a team. It's about making good decision for the player."

The All Blacks have called uncapped Richie Mo'unga into the squad as cover.

Source: AFP