Locky McCaffrey will start at no. 8 in place of the injured Pete Samu in the Brumbies' semi-final clash against the Jaguares.
Samu stayed in Australia after twinging a hamstring in the Brumbies' clash against the Sharks last weekend, with the club taking a cautious approach to his rehab.
McCaffrey comes into the starting no. 8 spot, combining with Rob Valetini and Tom Cusack in the back row.
The Brumbies have proven their backrow depth this season, with David Pocock, McCaffrey and Rob Valetini all injured at certain parts of the year and the luxury of brining in McCaffrey wasn't lost on coach Dan McKellar.
"It's always nice at this time of year to be able to maintain combination and we've been able to do that the last couple of months," he said.
"Obviously disappointed for Pete Samu who was outstanding in the first half last week against the Sharks but we're very fortunate to be able to bring in a quality player and leader of our team in Locky McCaffrey, who before injury himself was one of the form players in the competition.
"Locky's certainly across how we do things in this team and he'll be an important player on Friday night."
Murray Douglas comes onto a 6-2 bench for the match against an in-form Jaguares outfit.
Captain Christian Lealiifano will play his 150th Super Rugby match in the game, which could be his last depending on the result of this weekend's match, while prop Les Makin will notch his 50th.
McKellar said they were expecting a physical, forward-heavy battle against the South African conference-winning Jaguares.
"Traditionally the Argentinian sides are always strong around set piece, scrum, lineout maul and certainly a very physical side," he said.
"They've got big men throughout their team in their forward pack with Argentinian internationals across the board.
"We know we need to make sure we're effective and efficient throughout our set piece and that we turn up ready with physical intent because if we don't do that we won't get the result we're after."
The Brumbies are looking for an eighth straight win when they take on the Jaguares on Saturday morning with the winner to face off against either the Hurricanes or the Crusaders in the final.
Canberra could yet host the Super Rugby final, should the Brumbies win on Saturday morning and the Hurricanes get over the Crusaders on Saturday night.
If the top-seeded Crusaders win their Super Rugby semi-final, they will have the hosting rights.
The Brumbies face the Jaguares at Estadio Jose Amalfitani on Saturday June 29, kicking off at 9:05am AEST, LIVE on FOX SPORTS and Kayo.
TEAM
Brumbies to face Jaguares
1. Scott Sio
2. Folau Fainga’a
3. Allan Alaalatoa
4. Rory Arnold
5. Sam Carter
6. Rob Valetini
7. Tom Cusack
8. Lachlan Mccaffrey
9. Joe Powell
10. Christian Lealiifano ©
11. Toni Pulu
12. Irae Simone
13. Tevita Kuridrani
14. Henry Speight
15. Tom Banks
Reserves
16. Connal Mcinerney
17. James Slipper
18. Leslie Leuluaialii-Makin
19. Darcy Swain
20. Murray Douglas
21. Jahrome Brown
22. Matt Lucas
23. Tom Wright
