Costello has been hampered by injuries throughout 2019. He missed a loss to USC on Sept. 7 after being hurt in the season opener against Northwestern but returned to play in losses to UCF and Oregon amid the Cardinal's 1-3 start.
Davis Mills is expected to make his second start of the season, according to the school. Mills was 22-for-36 for 237 yards and a touchdown with one interception while filling in for Costello against the Trojans.
Costello has thrown for 471 yards and two touchdowns with two interceptions this season. He has completed 56.4% of his passes after completing 65.1% last season.