Dan McKellar is exploring his options at halfback after demoting Joe Powell for the first time this season ahead of the Brumbies' key Super Rugby match against the Jaguares.
Matt Lucas will be the starting No.9 in Buenos Aires on Sunday (AEDT), with the smooth-passing Powell having owned the jersey in all their nine games until now.
Lucas has had to be content with seven bench appearances but gets his chance inside skipper Christian Lealiifano, who continues his run of starting every game at five-eighth.
Coach McKellar has made one other starting switch from the team who bravely held out the Stormers 19-17 in Cape Town last week.
James Slipper replaces Scott Sio at prop, continuing the season-long rotation between the two seasoned looseheads.
There are two changes on the bench.
Hooker Conal McInerney was flown to Argentina to replace veteran Josh Mann-Rea, who suffered a suspected season-ending knee injury against the Stormers.
Irae Simone returns as reserve back cover, in place of Wharenui Hawera.
The Brumbies are chasing a third straight success on the road after season-reviving wins in South Africa, over the Lions and Stormers.
They take a 4-5 record into their clash with the Jaguares (4-4), who are coming off successive losses in South Africa, followed by a bye last week.