Big blow for Wallabies as Pocock ruled out

Australia's hopes of avoiding their worst ever world ranking have taken a major hit, with star flanker David Pocock ruled out of Saturday's vital Rugby Championship Test against South Africa.

Pocock failed a fitness test just prior to Friday's captain's run in Brisbane and is still yet to fully recover from the neck injury he sustained in the second Bledisloe Cup defeat in Auckland.

He has been replaced at No.8 by Pete Samu, who was not included in coach Michael Cheika's initial 23-man squad but will now start alongside captain Michael Hooper and Lukhan Tui in the back row.

Pocock is fearful for his longevity in the game after he was targeted by the All Blacks, who illegally twisted his neck in an attempt to remove him from the breakdown.

Hooper said to his knowledge, no other players were being tackled the same way, and he urged World Rugby to involve players in discussions around stamping out neck rolls.

"It's a significant injury and a significant issue," he told reporters on Friday.

"We sent in clips to World Rugby ... they've said it doesn't meet the red card threshold.

"I know, being in a similar position to David, you want to be protected and safe.

"It's now cost us David having to sit out and be concerned about a pretty vital part of your body and as a fellow player, you've got to sympathise with that."

Pocock's absence is a bitter blow given how important he is to the Wallabies, who are desperate to restore some pride after back-to-back beltings at the hands of New Zealand.

History is on their side - the Springboks have won only once in seven matches at Suncorp Stadium.

If the Wallabies were to lose, they would plummet to a record low of seventh in the World Rugby rankings.

Australia has never been below sixth since the rankings system was introduced in 2003.

"It's been a tough week," Hooper said.

"We've had to have some pretty honest conversations about how we're playing, how guys are going about their business on the field.

Samu will make his maiden Test start against South Africa, having come off the bench five times since making his debut earlier this year.

"He's been doing a great job in the cameos he's been having off the bench ... he's played in big games and he'll be itching to go."

WALLABIES: Israel Folau, Dane Haylett-Petty, Reece Hodge, Matt Toomua, Marika Koroibete, Kurtley Beale, Will Genia, Pete Samu, Michael Hooper (capt), Lukhan Tui, Adam Coleman, Rory Arnold, Allan Alaalatoa, Tatafu Polota-Nau, Scott Sio. Res: Folau Faingaa, Tom Robertson, Taniela Tupou, Izack Rodda, Ned Hanigan, Joe Powell, Bernard Foley, Jack Maddocks.

SPRINGBOKS: Willie le Roux, Makazole Mapimpi, Jesse Kriel, Damian de Allende, Aphiwe Dyantyi, Elton Jantjies, Faf de Klerk, Warren Whiteley, Pieter-Steph du Toit, Siya Kolisi (capt), Franco Mostert, Eben Etzebeth, Frans Malherbe, Bongi Mbonambi, Steven Kitshoff. Res: Malcolm Marx, Tendai Mtawarira, Wilco Louw, RG Snyman, Francois Louw, Embrose Papier, Handre Pollard, Cheslin Kolbe.