A shoulder injury looks set to keep flanker Brown sidelined for six weeks, which would rule him out of the domestic finals and potentially the start of the Trans-Tasman competition.

But his absence is offset by the return of vice-captain Tom Cusack and Wallabies winger Tom Wright for a clash with the battling NSW Waratahs at the Sydney Cricket Ground on Friday.

Cusack returns at flanker, Bayley Kuenzle comes onto the bench for his first game of the year, while Wright returns on the wing to push Mack Hansen back to the replacements list as the reigning champions launch a push for top spot and hosting rights for the final.

It makes Brown's injury a cruel blow given the Brumbies are beginning to see the light at the end of the tunnel following a debilitating period which left them to call on a raft of debutants in recent weeks.

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Brumbies coach Dan McKellar is wary of a Waratahs ambush following the sacking of NSW mentor Rob Penney, which came after five successive defeats to start the season including a record defeat at Canberra Stadium.

"We're still just waiting on final details there around scans, but it looks like six weeks-plus [for Brown], which is a shame," McKellar said.

"He was very good over pre-season and on the back of pre-season has had an excellent start to the year so it's a shame to lose him for a period of time.

"That's footy unfortunately, we've got Tommy Cusack fit and available and Rory Scott is at the start of his career and gets another chance.

"Wrighty has just got to turn up on Friday night and just do his job, and get the basics done well. He knows he hasn't played in a long time. If an opportunity in space comes, we know he is dangerous in that area of the game.

"Mack's been really good and he will get an opportunity in the last 25 to 30 minutes this week. We're starting to get players back which is good.

"It's good to get minutes into players who haven't had much opportunity this year."

McKellar expects Brumbies hooker Folau Fainga'a will have a point to prove after being left out of Dave Rennie's 40-man squad for a Wallabies camp at Sanctuary Cove this month.

Fainga'a was overlooked in favour of four other hookers, including Brumbies young gun Lachlan Lonergan who will come off the bench on Friday night.

But Rennie has left the door wide open for the likes of Fainga'a to force his way back into contention for Test football this year and the Brumbies could yet reap the rewards.

"A little bit of fire in the belly," McKellar said when asked about the response he expects from Fainga'a this week.

"Understand it's not the final squad list for the Bledisloe or the Rugby Championship. It's a group of players that will get together for a camp.

"A bit of a line in the sand there, I'm sure Dave has given them good feedback and no doubt, like any professional footballer or athlete, he'll have a competitive edge about him this week and want to prove a point which is good for the Brumbies."

SUPER RUGBY AU ROUND SEVEN

Friday: NSW Waratahs v ACT Brumbies at Sydney Cricket Ground, 7.45pm. Broadcast: Live on Stan Sport.

ACT Brumbies squad: 1. Harry Lloyd, 2. Folau Fainga'a, 3. James Slipper, 4. Nick Frost, 5. Cadeyrn Neville, 6. Rob Valetini, 7. Tom Cusack, 8. Pete Samu, 9. Nic White (c), 10. Noah Lolesio, 11. Andy Muirhead, 12. Irae Simone, 13. Len Ikitau, 14. Tom Wright, 15. Tom Banks. Replacements: 16. Lachlan Lonergan, 17. Fred Kaihea, 18. Sefo Kautai, 19. James Tucker, 20. Rory Scott, 21. Ryan Lonergan, 22. Bayley Kuenzle, 23. Mack Hansen.

NSW Waratahs squad: 1. Angus Bell, 2. David Porecki, 3. Harry Johnson-Holmes, 4. Jeremy Williams, 5. Max Douglas, 6. Hugh Sinclair, 7. Carlo Tizzano, 8. Will Harris, 9. Jake Gordon (c), 10. Will Harrison, 11. James Ramm, 12. Lalakai Foketi, 13. Izaia Perese, 14. Alex Newsome, 15. Jack Maddocks. Replacements: 16. Tom Horton, 17. Tetera Faulkner, 18. Darcy Breen, 19. Michael Wood, 20. Charlie Gamble, 21. Jack Grant, 22. Tane Edmed, 23. Mark Nawaqanitawase.

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