The 22-year-old is set to appear in his fifth Test, and first since October, after being named as a reserve in Mendoza.

Like he has done on so many occasions for the Brumbies, Lonergan will replace Folau Fainga'a when he is injected into the affair.

The elevation to the side came after Dave Porecki suffered a concussion at training earlier this week and Lonergan is looking to make the most of his opportunity.

"Getting more footy under my belt from Super Rugby this year will really benefit me going into this weekend," Lonergan said. "Last year I didn't have that much experience, I think it let me down a little. Hopefully this year it'll be better.

"Making an instant impact has been a big focus this week. They love getting in breakdowns, getting on the ball, so there will be a big focus. The breakdown will go a long way to winning the game."

Lonergan has developed significantly since making his Test debut last July, benefiting from exposure to both the Wallabies set up and increased playing time at the Brumbies.

Australian coach Dave Rennie has been impressed with his commitment despite sitting behind Porecki and Fainga'a in the Wallabies pecking order.

Sunday, he said, is a chance for Lonergan to make the No.16 jumper his own for the remainder of the Rugby Championship.

"Lachy's a really good footy player," Rennie said. "He's not the biggest man, but a good athlete. He's quick, got post-tackle presence, a very good thrower.

"We want him to come out and do what he's been doing all season. He's had to be patient and wait for his opportunities, he gets a chance to make a statement this weekend."

1. James Slipper (117 Tests)

2. Folau Fainga'a (28 Tests)

3. Allan Alaalatoa (55 Tests)

4. Darcy Swain (11 Tests)

5. Matt Philip (23 Tests)

6. Jed Holloway*

7. Michael Hooper (c) (121 Tests)

8. Rob Valetini (21 Tests)

9. Nic White (50 Tests)

10. Quade Cooper (75 Tests)

11. Marika Koroibete (45 Tests)

12. Hunter Paisami (17 Tests)

13. Len Ikitau (15 Tests)

14. Jordan Petaia (18 Tests)

15. Tom Wright (12 Tests)

Replacements

16. Lachlan Lonergan (4 Tests)

17. Matt Gibbon*

18. Taniela Tupou (40 Tests)

19. Nick Frost (2 Tests)

20. Rob Leota (9 Tests)

21. Pete Samu (22 Tests)

22. Jake Gordon (12 Tests)

23. Reece Hodge (55 Tests)

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