Michael Cheika says he has no fears about throwing young forwards into the fray against a physical Argentina pack after handing Lopeti Timani his run-on debut at Twickenham this Saturday.
Timani was competing with the Bath-based Leroy Houston for the Wallabies No.8 spot and replaces the injured Sean McMahon, who is expected to miss a month with syndesmosis picked up in last weekend's loss to South Africa in Pretoria.
Houston may yet earn a Test debut via the bench, which has yet to be finalised.
The towering Rory Arnold has also been drafted in at lock, where he will partner fellow young gun Adam Coleman, at the expense of Rob Simmons in the only other change to the starting line-up from the 18-10 defeat.
Simmons passed all concussion protocols after suffering a head knock against the Springboks but was axed as Cheika searches for the best combination.
In opting for the relative inexperience of Timani (one Test) and Arnold (four Tests), Cheika said the Wallabies could have no fear in backing young stars.
"We can't be frightened to do that. No matter what game it is, whether it's Argentina (or anyone else)," he said.
Timani, who came off the bench in the victory over Argentina in Perth last month in his only Test to date, would bring some much-needed size and aggressive running at Twickenham on Saturday, Cheika said.
With the versatile Dean Mumm - a lineout specialist - making his home at No.6, Cheika believes the Wallabies need a hard-runner at the back of the scrum in the mould of veteran Wycliff Palu.
"I think with the profile of the other players we have, like the sixes who are more the jumping-type sixes, that ball-carrying, Wycliff Palu-style No.8 is something that we want to have as well," Cheika said.
"We want to be able to do both. Leroy is quite an abrasive runner as well, so there's a great opportunity to (see) how he'll go with the step up."
Arnold has impressed off the bench, and Cheika hopes he takes this weekend is a chance to prove he deserves to be a long-term starter.
"He's just been aggressive, his lineout jumping has really improved, his mobility and ball carrying... and every time he's come onto the field from the bench he's made an impact as a finisher," Cheika said.
"I just think it's a real opportunity for him."
WALLABIES TEAM TO FACE ARGENTINA
15. Israel Folau, 14. Dane Haylett-Petty, 13. Samu Kerevi, 12. Bernard Foley, 11. Reece Hodge, 10. Quade Cooper, 9. Will Genia, 8. Lopeti Timani, 7. Michael Hooper, 6. Dean Mumm, 5. Adam Coleman, 4. Rory Arnold, 3. Sekope Kepu, 2. Stephen Moore (capt), 1. Scott Sio.