The 39-test flanker was ineffectual in the Brumbies' 27-22 home loss to the Durban-based Sharks on Saturday, a day after it was announced he would leave the club at the end of the season to play for Irish club Leinster.
Fardy's starting blindside spot will go to rookie Ben Hyne.
"That's a tactical decision, there's no injury there with Fards," Larkham told reporters on Wednesday.
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"That's just making sure that we maintain the motivation in the group and keep the energy out there in the field."
The Brumbies, the only Australian team to reach the playoffs last season, lost their opener away to the Canterbury Crusaders and a third successive loss against Perth-based Force would put their hopes of reaching the post-season in jeopardy.
Larkham said he hoped Fardy's omission would encourage the other senior players to step up as the Brumbies seek to revive their season.
"We've got a few leaders but if you look at the game last week it was a little bit disappointing at the end," he said.
"With Fards out now I guess you look to the other senior players and you expect them to take a little bit more onus on the motivation and the performance and the motivation of the team."
(Reporting by Ian Ransom; Editing by John O'Brien)
