Green finished with four tackles in what was his eighth game with the Aggies.
"Torrey stepped in and played well," Utah State coach Matt Wells said. "But that is part of the process when I say this team has to wrap its arms around everyone, everybody has to play a little better."
Anthony Williams, a transfer from Pierce junior college, is Green's backup and will also get more time, Wells said.
"The depth has taken a bit of a hit now," Wells said. "So it's good we have LT Filiaga, and Torrey played well and Anthony Williams. We will rally around the Vigil brothers, the secondary and anything else (defensive coordinator) Todd Orlando schemes up."
Nevertheless, it will be difficult to replace Fackrell. The junior was tabbed as one of the best linebackers in the Mountain West this year after a sophomore season in which he started every game and earned honorable mention Sophomore All-American honors by College Football News and second-team all-Mountain West honors. He led the Aggies with 13 tackles for loss, had two forced fumbles, five sacks and finished with 82 tackles on the year.
Wells was emotional when he spoke of the injury to Fackrell.
"It is tough for me as a head coach to know what that kid went through to be where he is," Wells said. "He is an extremely talented kid, great leader and teammate. It stinks, but it is the brute nature of football. But I hate it for him."
Fackrell, who hails from Mesa, Ariz., redshirted in 2011 but stands a good chance of receiving another year of eligibility since the injury took place in the first game of the season.
As for the immediate future, the Aggies at least have proven linebackers in brothers Nick and Zach Vigil and Filiaga, the Utah transfer.
Nick Vigil in particular impressed Wells in the loss to Tennessee after he led the team with 15 tackles.
"Nick absolutely belong on the field in that arena and environment with that SEC talent around him," Wells said.
Nick Vigil said he felt the linebackers could step up in Fackrell's absence, noting he was impressed with Green on Sunday.
"He knew what he was doing," Nick Vigil said. "He didn't get caught up in the moment. We need him to play well."
Idaho Stateat Utah State
O Saturday, 6 p.m.
TV • MW Network
Idaho State at Utah State
Saturday, 6 p.m.
TV/Web: Mountain West Network