AUSTRALIA have suffered a major setback ahead of Saturday night’s Test against Argentina with Wallabies’ captain Michael Hooper forced to pull out of the must-win match because of a hamstring injury.

Hooper was sidelined for two months after tweaking his hamstring in the series loss to Ireland and felt some pain in last weekend’s win over South Africa.

He was picked to play against the Pumas but after another scare at training the Wallabies coach Michael Cheika said he opted to play it safe and withdraw.

“He felt his hamstring a bit at training yesterday afternoon and with his recent history, we just thought it was best not to push it,” Cheika said.

“He was really keen to play this weekend but a week off will be a good thing for him to just get it right.”

David Pocock, who is also returning from injury, will move from the back of the scrum to replace Hooper at openside flanker as well as taking on the captaincy duties.

Pocock will lead the Wallabies for the first time since the Test win over France in Paris in 2016.

Just as he himself was a late withdrawal a week earlier, Pocock said Hooper had pushed to play until his body told him otherwise.

“He pulled up a bit sore from training (on Thursday). He got through the whole session but felt like he wasn’t quite good to go,” new skipper Pocock said.

“It’s a huge honour to serve the team in that role as captain. One of the things we’ve been working on as a team is to have a number of senior guys stepping up to support Hoops.

“I don’t think a huge amount changes, guys come in and out all the time.

“We’ve trained for that.”

It is the same hamstring that grounded Hooper from the NSW Waratahs after the damage was first sustained against Ireland in late June.

Pocock did admit that reverting from No.8 to No.7 as the solo openside specialist would mean “a slightly different role.”

“Pete Samu comes in at No.8 and he’s a great player. We saw how he stepped up last week (against South Africa),” Pocock said.

After the extra stress that dubious neck rolls have put on his body in an already highly combative position, Pocock said the neck troubles that forced him to miss last weekend’s Test against South Africa were being managed.

“It’s something we’ve got a plan for with the medical team and I got through a fair amount of contract on Thursday. I’m feeling confident with it,” Pocock said.

With Samu in the starting side, Ned Hanigan comes on to the bench.

Pocock warned that the Pumas had made big improvements under new coach Mario Ledesma, who was a coaching assistant for the pack at the Wallabies between 2015-17.

“They’ve done exceptionally well to mix that abrasive, big forward pack and good guys at the breakdown with the ability to turn it on (in attack),” Pocock said.

“One of the things they have begun to master is consistency.”

The “C” word is big in the Wallabies’ vocabulary too because only back-to-back Test wins will give their season some impetus.

Updated Wallabies team to play Argentina:
1. Scott Sio

2. Tatafu Polota-Nau

3. Allan Alaalatoa

4. Rory Arnold

5. Izack Rodda

6. Lukhan Tui

7. David Pocock (c)

8. Pete Samu

9. Will Genia

10. Kurtley Beale

11. Marika Koroibete

12. Matt Toomua

13. Reece Hodge

14. Israel Folau

15. Dane Haylett-Petty

Reserves
16. Folau Faingaa

17. Sekope Kepu

18. Taniela Tupou

19. Adam Coleman

20. Ned Hanigan

21. Nick Phipps

22. Bernard Foley

23. Jack Maddocks