Maro Itoje returns as captain for the Canberra showdown to lead a starting XV full of players considered first choice in their positions, including half-backs Jamison Gibson-Park and Finn Russell.
The fixture with the Brumbies is being treated by Farrell as a dry run for the series opener against the Wallabies on July 19.
But he insisted his Lions stars still have to earn the jersey after leaving the door open for others to stake their claim, with Saturday's match against an AUNZ Invitational XV the final opportunity to impress.
"The truth of the matter is we have got a good side that's going to take the field on Wednesday and I will tell you what I said to the team," the head coach said.
"There's always going to be speculation, but it's up to people to put their best foot forward for a Test spot from now on in with regards to the chance they have got on Wednesday and on Saturday.
"Players can play themselves in and players can play themselves out, but we are looking for a cohesive team performance and that is what we are trying to achieve.
"There has to be movement in selection. The nature of the format of these two games allows for us to be open-minded.
"We play on Saturday after this and have a full week's worth of training, so you have to stay open-minded. A closed book is not good for anyone.
"I wouldn't call it a blank slate, you have always got ideas, but you need to leave wriggle room for things to unfold and make a judgement on what you see over the next couple of games."
Providing X-factor on the bench are back row Henry Pollock and versatile playmaker Marcus Smith in an opportunity for both England stars to prove they are viable options against Australia.
In normal circumstances flanker Tom Curry and prop Tadhg Furlong would be assured of Test places, but they need big games following underwhelming tours so far.
Prop Ellis Genge, flanker Ollie Chessum and full-back Blair Kinghorn must also put their best foot forwards amid fierce competition for places. The likes of Dan Sheehan, Itoje, Gibson-Park, Russell and Jack Conan are nailed-on starters.
After a disappointing performance against the New South Wales Waratahs on Saturday, the Lions are looking to build momentum before heading to Adelaide for their penultimate midweek game.
The Brumbies were the only provincial side to beat the Lions in 2013 and are dangerous opponents.
"There is a real sense of excitement because there's a lot of history that goes with this fixture," Farrell said.
"The last two occasions we have played the Brumbies there have been four points in it, for and against. We know the challenge ahead and it's something we have been looking forward to."
