Polota-Nau aggravated the injury against England on Tuesday
Australia hooker Tatafu Polota-Nau has been ruled out of Saturday's second Test against England through injury.
Polota-Nau missed the win over England last Saturday with an ankle problem and aggravated the injury in the Australian Barbarians' loss to England on Tuesday.
The Wallabies, who name their team on Thursday, are also without first-choice props Benn Robinson and Ben Alexander, plus senior hooker Stephen Moore.
Their absence was noticeable as England dominated the scrums in the first Test.
The quartet of absences forced Australia coach Robbie Deans to name the most inexperienced Australian front row in 27 years and England's dominance up front earned them two penalty tries in Perth.
Deans had hoped to name a more experienced front-row for Saturday's encounter in Sydney, but his hopes have been dashed by the recurrence of Polota-Nau's ankle problem.
Deans will now choose between Saia Faingaa, who started the first Test at hooker, and Huia Edmonds for the number two shirt, while props Salesi Ma'afu and Ben Daley could retain their places in the starting XV.
Australia lock Dean Mumm admitted the Wallabies' pride had been dented by their scrummaging performance at the Subiaco Oval.
"It was obviously a knock to us to have an area of our set piece not go well," said Mumm.
"The fact is the scrum does matter and we are working hard to try and get the best out of it. Our pride is a little bruised. We are doing as much as we can to try and fix that up.
"We are excited about the challenge in front of us. It's a substantial one and they certainly have the points on the board. We are looking to rectify that."
Forwards coach Jim Williams admitted the home side must be more physical to match the English pack.
"It's just got to be ramped up again this week. The physicality of the England team, especially in their tight play, was enormous," said Williams.
We knew the scrum would be very important last week but it is not the be all and end all
"The physicality that these guys play in the English Premiership and the Six Nations is just relentless and we need to make sure that we meet that battle head on."
England also name their team on Thursday, with prop Dan Cole insisting they have learned they cannot afford to rely solely on a dominant set piece to beat Australia on Saturday.
Hooker Steve Thompson described England's performance as "rope-a-dope" because they became obsessed with hammering away at the scrum and paid the price elsewhere.
England missed upwards of 30 tackles and their attacking game was a shadow of the incisive rugby played by Wallabies fly-half Quade Cooper, who ended up with two tries.
"It would be a dangerous thing to imagine the scrum would just win the game," said Leicester tight-head Cole.
"We knew the scrum would be very important last week but it is not the be all and end all, there is a game outside the scrum and they were obviously better than us.
"We've got to sharpen up. When we did get the ball we kicked it straight back to them to play at us on the counter-attack.
"We were sloppy. We've had to analyse ourselves and be pretty brutal, individually and as a team, and put those things right."