Tuel has seen significant playing time coming off the bench the last two weeks in place of the turnover-prone Halliday. For the season, Tuel has completed 95 of 145 passes for 908 yards, five touchdowns and three interceptions.
Halliday has completed 109 of 206 passes for 1,348 yards and nine touchdowns, but has thrown a conference-worst 11 interceptions.
"The biggest thing is who moves the team the best," Leach said. "We've had some inconsistency around here. We'll see what they do here in practice."
Tuel has been ticketed for first-string reps when the team convenes today for its first of two practices during this bye week.
The Cougars (2-5 overall, 0-4 Pac-12) have struggled in the past through quarterback controversies, notably in 1990 when players were divided between holdovers Aaron Garcia and Brad Gossen and true freshman Drew Bledsoe. But that does not appear to be the case this year, and Leach said both signal-callers have handled the competition well from an emotional standpoint.
"I think they're fine emotionally," Leach said. "As far as the field, it's been inconsistent. That's why we're where we're at."
"Not really," he said. "It's talented and good. Each team is explosive in some fashion or another."