Brumbies recruit Matt Giteau will miss the clash with Western Force after failing to overcome a quadriceps injury.

Giteau, who sustained a strain in his left leg nearly three weeks ago, was ruled out by medical staff today.

The 27-year-old is expected to be available for his side's round two clash against the Bulls in Pretoria.

"I'm obviously very disappointed as it was a game I was really looking forward to," Giteau said.

"You want to be available for the first game of the season and when you've got history (with the Force) like I do, it was a match I was really keen to be a part of.

"But I said from the outset that I wouldn't play if my injury was going to jeopardise the performance of the team. As it happens, that decision has now been made and I'll now start my preparation for the Bulls."

Giteau backed replacement Matt Toomua to shoulder the playmaking responsibilities in his absence.

"Matty and Christian (Lealiifano) were impressive at 10 and 12 last week (against the Waratahs)," he said.

"They've trained well again in those positions this week and they're forming a strong combination there."

Coach Andy Friend says both coaching and medical staff eventually opted to err on the side of caution.

"Matt's one of the best fly-halfs in the world so we were keen to give him every opportunity to play," Friend said.

"While he did respond well to his rehabilitation, the decision was made not to risk aggravating the injury and sidelining him for an extended period.

"It was always going to be touch-and-go. When he originally strained his quad we were told it was a 21-day recovery and he had 19 days to the Force match. As it turns out, he'll now receive an additional eight days before his first match of the season in Pretoria."