Chryst, who took over as the starter midway through the 2016 season, suffered what appeared to be a head injury early in the Cardinal's 58-34 win against UCLA on Sept. 23, and did not dress for last week's win against Arizona State.
With Chryst sidelined, Costello stepped in and the Stanford offense has operated at a more efficient level. The Cardinal scored touchdowns on their final seven drives against UCLA and finished the game with 553 yards of offense and amassed 501 yards against ASU.
In the previous two games with Chryst under center, Stanford lost twice -- 42-24 to USC and 20-17 to San Diego State -- and highly touted running back Bryce Love seemed underutilized. On the year, Chryst has competed 39-of-75 passes (52.0 percent) for 509 yards with four touchdowns and two interceptions.
Costello is 33-of-52 for 376 yards (63.5) with three touchdowns and no picks.
Utah's quarterback situation is also unclear. Starter Tyler Huntley was injured against Arizona on Sept. 22, and all signs point to his backup and last year's starter, Troy Williams, getting the start against Stanford.