Vigil had 11 carries for 51 yards Saturday before he left the game in the third quarter with the injury.
Logic says if Vigil can play, he would get most of the snaps at linebacker, but Utah State coach Matt Wells hinted that may not be the case, noting the Aggies have a big stable of linebackers but not running backs.
"It's next man up if he can't play," he said. "We'll see how he is later this week."
Regardless of Vigil's availability, Wells said the Aggies would stick with their game plan of focusing on the run game to help out Myers, who will be making his first start.
Myers replaced Harrison in the third quarter and finished 3-of-5 passing for 45 yards and rushed three times for 28 yards.
"I was proud of the job Kent did," Wells said. "Craig had a solid game up to that point with the touchdowns, no picks."
The Aggies are waiting on more medical results that will determine whether Harrison can return this season, but Wells didn't sound hopeful. As for Garretson, who suffered a wrist injury in the loss at CSU, he is definitely out after doctors discovered during his surgery that the injury was worse than expected.
Wells laughed at the absurdity of the situation and noted neither Myers nor his backup, freshman DJ Nelson, had not taken snaps with the first team until last week.
"At least Craig had the experience of spring ball before and other times," Wells said. "These guys don't have a tremendous amount of reps to draw from."
Myers, from Rowlett, Texas, attracted Wells' attention with his dual threat abilities. He is a better passer now than he was in high school, but the Aggies don't expect any heroics from him against Hawaii, Wells said.
"He doesn't need to win the game," Wells said. "He just needs to make smart decisions and be stingy with the football. The game hasn't changed and it will not change."